Math 4

Exercise 5.6

1. Convert into rupees. (using 100 p = 1 rupee)

a. 20 paise b. 8 paise c. 35 paise
f. 35 rupees 20 paise
d. 5 rupees 30 paise e. 2 rupees 15 paise

g. 65 rupees 60 paise

2. Convert into paise (using 1 rupee = 100 paise).

a. 0.3 rupees b. 0.35 rupees c. 0.85 rupees

d. 2.75 rupees e. 5.85 rupees f. 7.15 rupees

g. 3.64 rupees h. 2.24 rupees i. 9.65 rupees

3. Convert into metre (m) (using 100 cm = 1m).

a. 10 cm b. 20 cm c. 25 cm

d. 85 cm e. 96 cm f. 2m 30 cm

g. 5 m 65 cm h. 8 m 26 cm i. 8 m 32 cm

4. Convert into centimetre (cm) (using 1 m = 100 cm).

a. 0.8 m b. 0.6 m c. 0.32 m d 0.68 m
h.8.34 m
e. 2.36 m f. 5.24 m g.0.09 m

5. Convert into kilogram (kg). (using 1000 gm = 1 kg).

a. 6 gm b. 350 gm c. 640 gm d. 2 kg 250 gm

e. 5 kg 450 gm f. 6 kg 320 gm g. 12 kg 600 gm h. 20 kg 550 gm

6. Convert into gram (gm). (using 1 kg = 1000 gm).

a. 0.02 kg b. 0.324 kg c. 2.356 kg d. 1.24 kg e. 8.75 kg f. 6.86 kg

7. Convert into litre (l). (using 1000 ml = 1l).

a. 5 ml b. 25 ml c. 320 ml d. 560 ml
h. 10 l 200 ml
e. 3 l 65 ml f. 5 l 350 ml g. 8 l 600 ml

8. Convert into millilitre (ml).

a. 0.5 l b. 0.2 l c. 0.85 l d. 0.32 l
g. 3.2 l h. 5.27 l i. 6.84 l
e. 1.6 l f. 2.5 l

Consult your teacher.

Oasis School Mathematics Book-4 151

Worksheet

Aadhya's shopping

Aadhya bought 3 1 kg of rice, 4.50 kg of
2

sugar and 300 gm of pea.

weight of rice in decimal = kg

weight of sugar in fraction = kg

weight of pea in fraction kg

weight of pea in decimal kg

She also bought 500 cm of cloth and 300
cm of ribbon.

length of cloth = cm = m

length of ribbon = cm = m

She also bought 300 ml of oil and 1 litre
2

of milk.

capacity of oil = ml = l

capacity of milk = litre

= ml

152 Oasis School Mathematics Book-4

Objective Questions

Colour the correct alternatives.

1. The number 7 is
10

Seven tenths Seven tens Seven
hundreds

2. The fraction 16 is equal to
100

0.25 0.16 0.08

3. 7 ones + 2 tenths + 3 hundredths + 8 thousandths is equal to

0.7238 7.238 72.38

4. Place value of 4 in the number 0.6341 is 4
10
4 4
1000 100

5. The value of 0.5623 × 1000 is equal to

56.23 562.3 5.623

6. The value of 0.215 × 7 is equal to

1.505 15.05 150.5

7. The value of 72.54 ÷ 100 is equal to

7.254 725.4 0.7254

8. 2 litre 400 ml is equal to

2.4 litre 2.04 litre 2.004 litre

9. The meaning of number 0.34 is same with the number

0.034 0.340 0.304

10. 5m 20 cm is equal to 5.02 m 5.002m
5.2 m

Number of correct answers

Oasis School Mathematics Book-4 153

Unit Test Full marks -20

1. Write the following in fraction and then in decimal: 3

a. Five hundredths 3
2
b. Seventy five and five tenths 3

c. One hundred twenty five and six tenths five hundredths

2. Write the place value of coloured digit:

a. 0.97 b. 48.178 c. 12.86

3. Write the following decimals in expanded form:

a. 56.75 b. 123.842

4. Add or subtract:
a. 16.09 + 31.631 b. 23.65 + 0.86 + 4.06 c. 164.92 - 85.631

5. Multiply: 3
a. 0.034 × 8
b. 0.012 × 100 c. 0.375 × 10

6. Divide: 3
a. 0.452 ÷ 4
b. 5.72 ÷ 7 c. 0.846 ÷ 10

7. a. A man walks 382.63 m in the morning and 324.68 m in the evening.

How much distance does he walk in all? 1.5

b. The length of a rope is 3.45 m. What is the length of 5 such
ropes? 1.5

154 Oasis School Mathematics Book-4

UNIT

6 Percentage and
Unitary Method

12 Estimated Teaching Hours: 15
93

6

Contents • Definition of percentage

• Conversion of fraction into percentage and
vice-versa

• Conversion of decimal into percentage and
vice-versa

• Percentage of given quantity

• Unitary method

Expected Learning Outcomes

Upon completion of the unit, students will be
able to develop the following competencies:

• To understand the concept of percent
• To understand the relation of fraction and percentage
• To convert the fraction into percentage and vice-versa
• To convert the decimal into percentage and vice-versa
• To solve the simple verbal problems of percentage related to our

daily life
• To calculate the value of many items if the unit value is given
• To calculate the unit value if the value of many items is given

Materials Required: Graph sheet

Oasis School Mathematics Book-4 155

Percentage

Look and lea rn. per cent

for every hundred

Per cent is composed of two words per and cent. Per means ‘for every’ and
cent means out of hundred. So per cent means out of every hundred.

I got 80% marks. I got 75 % marks.

Ram got 80 marks out of Shyam got 75marks out
100 full marks. of 100 full marks.

The symbol of per cent is % or p.c.

Relation of fraction and percent

In the given figure, a square is divided into

100 equal parts.
Fraction of the shaded parts = 11050.
Here, 15 out of 100 parts are shaded.

Percent of shaded part = 15%

Hence, 15 = 15%. I understand !
100

5 = 5%, 15 = 15%,12000 = 20%,18050 = 85%
100 100

To convert per cent into fraction, follow the steps given below.

Steps:
• Remove the percent symbol.
• Divide it by 100.
• Simplify the fraction into its lowest term.

156 Oasis School Mathematics Book-4

Example :

Convert 20% and 45% into fractions: Try

Solution: 20 % = 20 1 Remove % sign and divide it by 100 Convert into
100 5 Simplify it into its lowest term fraction

= 1 80% =
5

45 % = 45 9
100 20

= 9
20

Conversion of fraction into percentage

To convert the fraction into percentage, follow the steps given below.
Try
Steps:
Convert fraction into
• Multiply the fraction by 100

Example : • Put the symbol % percentage:

2 = 2 × 100% = 40% 3 =
5 5 10

1 = 1 × 100% = 10%
10 10

Conversion of decimal into percentage

To convert the decimal into percentage, follow the following steps.
Try
Steps:
Example : • Multiply the decimal by 100. Convert decimal into
• Put % symbol. percentage :

0.45:

Convert 0.25 into percent.

0.25 = 0.25 × 100 %

= 25 %

Conversion of percentage into decimal

Conversion of percentage into decimal Try

Steps: Convert percentage
• Remove the symbol %. into decimal:
• Divide it by 100.
80% =

Convert 60 % into decimal.
60
60 % = 100 = 0.6

Oasis School Mathematics Book-4 157

Exercise 6.1

1. Write the fraction and percentage of the shaded parts of the given figures
having 100 squares:
a. b.

2. Write the percentage in each of the following cases:
a. Akriti gets 55 marks out of 100 full marks.

b. Prakriti spends Rs 80 out of Rs 100.

c. 65 students are boys out of 100.
3. Express the following fractions in percentage.

a. 15 b. 30 c. 68 d. 79 e. 56
100 100 100 100 100

4. Write the fraction represented by the given figure and convert them
into percentage.

a. b. c.

5. Expressthefollowingfractionsinpercentage.

a. 3 b. 2 c. 4 d. 15 e. 3
4 5 20 20 50

f. 8 g. 15 h. 7
30 50 10

6. Express the following percentage in fraction.

a. 20% b. 35% c. 25% d. 30% e. 50%

f. 80% g. 75% h. 65%

7. Express the following decimal in percentage.
a. 0.5 b. 0.6 c. 0.35 d. 0.16 e. 0.46 f. 0.02 g. 0.07

8. Express the following percentage in decimal.
a. 10% b. 30% c. 80% d. 35% e. 5% f. 2% g. 45% h. 50%

9. a. Aadhya scored 85 out of 100 full marks. Express her marks in
percentage.

158 Oasis School Mathematics Book-4

b. Out of Rs. 40 from his pocket money, a boy spent Rs. 10. Express
this in percentage.

c. In a class of 25 students, 20 are present. Find the percentage of
present students.

Consult your teacher.

To find the percentage of given quantity

To find the percentage of given quantity, follow the following steps.

Example :

To find the value of 20% of 80. Steps:
Solution: 20% of 80
• Express the given percentage in
fraction

= 20 1 × 16 • Multiply the fraction by the given
100 5 quantity

= 16

Example :

Out of 80 students in a class, 40% are boys. Find the number of boys.

Solution: Total students = 80

Percentage of boys = 40% I can cancel equal number of
zeros from numerator and
Number of boys = 40 % of 80 denominator.

= 40 × 80
100

= 4 × 8 = 32

Exercise 6.2

1. Find the value of:
a. 20% of 120 b. 5% of 200 c. 15% of 300 d. 30% of 500 e. 40% of 240
f. 60% of 500 g. 5% of 150 h. 10% of Rs 500 i. 15% of Rs 700

2. a. In a class, there are 50 students. If 10% students are absent, find the
number of absent students.

b. Out of Rs. 80, a boy spent 20% of his money. How much money did he
spend?

c. Out of 50 students in a class, 60% are girls, find the number of girls.

Answers:
1. a. 24 b.10 c. 45 d. 150 e. 96 f. 300 g. 7.5 h. 50 i. 105
2. a. 5 b. Rs. 16 c. 30

Oasis School Mathematics Book-4 159

Unitary method

Unit means one. The word unitary is derived from the word unit. In this
chapter, we will learn the process of finding the value of a unit from the
value of many items and the value of many items from the value of a unit.

To find the values of many items when the value of a unit is given

Cost of one orange is Rs. 5 Multiplication is the repeated
Cost of 2 oranges = Rs. 5 + Rs. 5 = Rs. 2 × 5 addition.
= Rs. 10.

Cost of 3 oranges = Rs. 5 + Rs. 5 + Rs. 5
= 3 × Rs. 5
= Rs. 15

Cost of 1 copy = Rs 6 My logic,
Cost of 2 copies = Rs 2 × 6 = Rs 12 Value of many items = unit
Cost of 3 copies = Rs 3 × 6 = Rs 18 value × number of items
Cost of 4 copies = Rs 4 × 6 = Rs 24

Example :

Cost of one pencil is Rs. 6. What is the cost of 8 pencils?

Solution:

Cost of one pencil = Rs. 6

Cost of 8 pencils = 8 × Rs. 6

= Rs. 48.

To find the value of one item if the value of many items is given:

Cost of 5 pens is Rs. 100 If the value of many is given, divide
Cost of 1 pen is Rs. 100 ÷ 5 the total value by number of items
= Rs. 20. to obtain the unit value.
\ Cost of 1 pen is Rs. 20.

Value of one item = value of
many items ÷ number of items

160 Oasis School Mathematics Book-4

Example :

The cost of one dozen copies is Rs. 84. What is the cost of one copy?

Solution:

Cost of one dozen copies = Rs. 84 1 dozen = 12
Cost of 12 copies = Rs. 84

Cost of 1 copy = Rs. 84 ÷ 12

= Rs. 7

\ Cost of 1 copy is Rs. 7.

Class Assignment

1. Complete the given table:

Articles Unit cost Cost of 2 units Cost of 3 units
Banana Rs. 5 Unit cost
Apple Rs. 7
Orange Rs. 8

2. Complete the given table:

Number of Total cost
articles

4 Rs. 72

5 Rs. 360

6 Rs. 216

7 Rs. 217

10 Rs. 550

Exercise 6.3

1. a. If the cost of an article is Rs 25, what is the cost of 12 such articles?
b. If the cost of a pen is Rs 30, what is the cost of a dozen pens?
c. If one book has 135 pages, how many pages do 7 such books have?
d. A man runs 8 km in one hour. How far does he run in 24 hours?
e. There are 12 pencils in one dozen. How many pencils are there in 8 dozen?
2. a. If the cost of 8 kg of rice is Rs 320, what is the cost of one kg of rice?
b. If the cost of 10 balls is Rs 360, what is the cost of one ball?

Oasis School Mathematics Book-4 161

c. A car covers 480 km in 8 hours. How much distance does it cover in an
hour?

d. If 12 kg of sugar costs Rs 480, what is the cost of 1 kg of sugar?
e. 12 m of cloth costs Rs 750. What is the cost of 1m cloth?

Answers:
1. a) Rs. 300 b) Rs. 360 c) 945 pages d) 192 km e) 96 pencils
2. a) Rs. 40 b) Rs. 36 c) 60 km d) Rs. 40 e) Rs. 62.50

Further problems related to unitary method

In our daily life, we also face both the situations together where we have to
find unit value as well as the value of many items together.

Example :

The cost of 8 copies is Rs. 176. What is the cost of 5 such copies?

Solution:

The cost of 8 copies = Rs. 176 8 ) 176 (
22
The cost of 1 copy = Rs. 176 I know ! At first I have to
8 - 16 find the unit value then the
= Rs. 22
16 value of given quantity.

The cost of 5 copies = 5 × R.s 22

= Rs. 110 - 16

\ Cost of 5 copies = Rs. 110. 0

Exercise 6.4

Solve the following problems.
1. The cost of 10 biscuits is Rs 130. What is the cost of 6 such biscuits?
2. 30 metres of cloth costs Rs 1800. What is the cost of 5 m of cloth?
3. A man earns Rs 950 in 5 days. How much does he earn in 15 days?
4. Arpana earns Rs 3660 in a month. How much does she earn in 12

days?
5. A worker earns Rs 5670 in a week. How much does he earn in 12 days?

Answers:
1. Rs. 78 2. Rs. 300 3. Rs. 2850 4. Rs. 1464 5. Rs. 9720

162 Oasis School Mathematics Book-4

Worksheet

Write the marks obtained by your 20 friends in the unit test of this chapter.
Write the marks in fraction and convert them into percentage.

F.M - 20 Class IV
Section:

Name of students Marks Fraction Percentage
obtained

Oasis School Mathematics Book-4 163

Objective Questions

Colour the correct alternatives.

1. Prithak scored 80% marks in Mathematics means

he scored 80 out of 100

he scored 100 out of 80

he scored 80 out of 80

2. 0.25 is not equal to 25 25
25% 100

3. 60%

Percentage of the shaded part in the above figure is

50% 40%

4. 80% is equal to 0.08 8
4 20 100
5
160
5. 20% of 800 is equal to

200

6. If the unit value is Rs. 30, the value of 5 items is

Rs 30 ÷ 5 Rs 30 × 5 Rs 30

7. If the cost of 9 kg sugar is Rs 450, then the cost of 1 kg sugar is

Rs. 4050 Rs. 450 Rs. 50

Number of correct answers
164 Oasis School Mathematics Book-4

Unit Test Full marks -18

1. Write the percentage and fraction of the shaded part: 2
a. b.

2. Complete the given table: 2
Cost of 2 units
Articles Unit cost
Pen Rs. 25
Copy Rs. 20

3. Convert as mentioned: 4

a. 20% into fraction

b. 0.07 in percentage

c. 25% into decimal

d. 3 into percentage
20

4. Calculate the value of: 2

a. 20% of 300 b. 25% of 250

5. Solve the following problems: 4×2=8

a. Out of Rs. 80 from his pocket money, Ram spent Rs. 20. Express this

in percentage.

b. In a class there are 60 students. If 10% students are absent, find the

number of absent students.

c. A car covers 480 km in 6 hours. How long distance does it cover in

1 hour?

d. A man earns Rs. 750 in 5 days. How much does he earn in 8
days?

Oasis School Mathematics Book-4 165

UNIT

7 Time

12 Estimated Teaching Hours: 15
93

6

Contents • Time in hours and minutes
• A.M and P.M.
• Calendar
• Conversion of time
• Addition and subtraction of time

Expected Learning Outcomes

Upon completion of the unit, students will be
able to develop the following competencies:

• To tell the time in hours and minutes
• To know A.M and P.M.
• To read the calendar and to write the date in short form
• To convert the time into different units
• To add and subtract time

Materials Required: Clocks, Paper model of clocks, Calendar, etc.

166 Oasis School Mathematics Book-4

Time in hours and minutes

This is a clock. The face of the clock is marked with the
numerals 1 to 12 in equal intervals.
There are 5 sub-divisions between two numbers.

Each small division represents one minute; i.e. minute hand takes one minute
to move from one small mark to the next mark. The minute hand takes one
hour to make one complete rotation.

• A clock is marked with 12 numbers 1 to 12.
• There are 5 divisions between two successive numbers.
• Minute hand takes 1 minute to move from one mark to another
• 1 hour = 60 minutes.

Telling time
Position of both hands of the clock denotes time. Position of hour
hand directly shows hour. The minute hand shows minutes.

To find the minutes, check the position of minute hand by
counting the smaller divisions.

Hour hand is between 3 and 4.
Minute hand is at second division between 5 and 6. Therefore the time is 27
minutes past 3 i.e. 3:27.

Exercise 7.1 c.

1. Write the time shown on each clock face:
a. b.

d. e. f.

Oasis School Mathematics Book-4 167

2. Draw the minute hand to show the given time in each clock face.
a. b. c.

2 : 22 6 : 38 52 minutes past 8

3. Draw the clock to show the given time.
a. 5 :15 b. 23 minutes past 9 c. 8 : 38 d. 8 minutes past 10

e. 9 : 27 f. 42 minutes past 6

Consult your teacher.

A.M. and P.M.

Time from one midnight to another midnight is called a day. It takes 12
hours to complete one rotation by hour hand. Hour hand makes two complete
rotations in a day.

\ 1 day = 24 hours

Time from 12 midnight to 12 midday is denoted as A.M.
Time from 12 midday to 12 midnight is denoted as P.M.

7 A.M. means 7 o’clock in the morning. Remember !
4 : 30 A.M. means 4 : 30 in the morning.
5 : 15 P.M. means 5 : 15 in the evening. • 12 o’clock in the day time is 12 : 00 noon.
9 : 20 P.M. means 9 : 20 in the evening.
• 12 o’clock at night is 12 : 00 midnight.

• 12 o’ clock is neither A.M. nor P.M.

Exercise 7.2

1. Write the following times using A.M. or P.M.

a. 8 o’clock in the morning b. 7 : 15 in the evening

c. half past 6 in the morning d. 2 : 30 at night

e. 4 : 30 in the afternoon f. 9 : 45 in the morning

2. Write the time in am or in p.m. b.
a.

Day Evening

168 Oasis School Mathematics Book-4

c. d.

Morning Morning

3. Write your time table in A.M. and P.M.

a. wake up time b. time to take breakfast

c. time to go to school d. tiffin time

e. time to return home f. time to take dinner g. time to sleep

4. What time was it before 2 hours?

a. 12 : 00 noon b. 3 : 00 P.M. c. 1 : 00 P.M. d. 6 A.M.
d. 11 P.M.
5. What time will it be after 3 hours?

a. 12 : 00 midnight b. 5 : 00 P.M. c. 10 A.M.

Consult your teacher.

Calendar

Reading of calendar

We are already familiar with English and Nepali months.

January, February, March, April, May, June, Baisakh, Jestha, Ashad, Shrawan, Bhadra,
July, August, September, October, November Ashoj, Kartik, Mangsir, Paush, Magh, Falgun
and December are the English months in order. and Chaitra are the Nepali months in order.

Class Assignment

Let’s observe the calendar of November 2015.

Number of Fridays in this I know how to read
month is ............. the calendar.

Number of Saturdays in
this month is .............

The first day of this month
is.............

19th of November is.............

25th of November is.............

Oasis School Mathematics Book-4 169

Let’s observe the calendar of Shrawan 2072.

Number of Sundays in Shrawan 2072 is ...........
Number of Mondays in Shrawan 2072
is.............
21st Shrawan is..............
12th Shrawan is .............

Date in short form 12th April 2011 I know Falgun is the 11th
2066 Falgun 20 2011 / 4 / 12 Nepali month and April is 4th
2066 / 11 / 20 year / month / day
year / month / day English month.

Class Assignment

Write the following date in the short form:

2072 Poush 16 ........................ 19th March 2014 .......................

2071 Bhadra 13 ....................... 25th December 2012 .......................

2062 Ashad 12 ....................... 26th June 2015 .......................

2067 Chaitra 8 ....................... 29th August 2016 .......................

2072 Ashwin 3 ......................... 1st January 2020 .......................

Exercise 7.3

1. Write the names of 12 Nepali months in order.
2. Write the names of 12 English months in order.
3. Write the names of 7 days of a week.
4. Study the given calendar and answer the questions based on it.

 Which month of which year?
 How many days are there in this month?
 How many Sundays are there in this month?
 Which day is 13th of this month?
 Which day is the last day of the month?
 Which day is the 1st of Magh?

170 Oasis School Mathematics Book-4

5. Study the given calendar and answer the questions based on it.

 Which month of which year is in the given
calendar?

 How many days are there in this month?
 How many Mondays are there in this month?

v Which day is 20th May?
 Which day is the last day of the month?
 Children fun festival starts from 12th of this

month and it runs for 3 days. On which day
will it be over?
 Which day is the 30th April?

6. Write the following dates in short form: c. 2067 Magh 29
a. 2069 Jestha 14 b. 2064 Shrawan 12

d. 12th March 2015 e. 18th September 2016 f. 11th June 2014

7. Which days are represented by these Nepali dates?

a. 2072 / 4 / 6 b. 2071 / 5 / 13 c. 2062 / 2 / 14

8. Which days are represented by these English dates?

a. 2015 / 3 / 10 b. 2014 / 5 / 14 c. 2013 / 5 / 31

Consult your teacher.

Conversion of time
We can convert the unit of time into one another by using the
following relations.

1 year = 12 months 1 week = 7 days 1 minute = 60 seconds
1month = 30days 1 day = 24 hours 1 hour = 60 minutes
1 year = 365 days
To convert year into month,
Let’s see some examples. multiply year by 12.
Example 1:
Convert 2 years 5 months into months
Solution:
2 years 5 months
= 2 × 12 months + 5 months
= 24 months + 5 months
= 29 months

Oasis School Mathematics Book-4 171

Example 2: To convert month into day, multiply
Convert 5 months 20 days into days month by 30.
Solution:
5 months 20 days \ 5 months = 5 × 30 = 150 days

= 5 × 30days + 20 days

= 150 days + 20 days

= 170 days

Example 3: To convert hours into minutes,
Convert 7 hours 32 minutes into minutes. I have to multiply hour by 60.
Solution: 7 hours = 7 × 60 minutes
7 hours 32 minutes = 420 minutes
= 7 × 60 minutes + 32 minutes
= 420 minutes + 32 minutes
= 452 minutes.

Example 4: To convert minutes into hours,
divide minutes by 60.
Convert 135 minutes into hours and minutes.
60 ) 135 (2 hours
Solution : - 120
15 minutes
135 minutes
Quotient represents hours and
= 135 hours remainder represents minutes.
60

= 2 hours 15 minutes

Example 5: To convert months into year, I
Convert 38 months into year and month. have to divide months by 12.

Solution:

38 months

= 38 years 12 ) 38 (3 year
12 - 36
2 months
= 3 years 2 months
38 months = 3 years 2
months

172 Oasis School Mathematics Book-4

Exercise 7.4

1. Convert the following into months:

a. 2 yrs. b. 2 yrs 5 months c. 3 yrs
f. 5 yrs 7 months
d. 3 yrs 3 months e. 4 yrs 2 months
c. 3 months 20 days
2. Convert the following into days:
c. 2 weeks 3 days
a. 3 months b. 2 months 15 days
c. 2 days 10 hours
d. 4 months 16 days e. 5 months 7 days f. 9 days 3 hours
c. 5 hours 15 minutes
3. Convert the following into days: f. 4 hours 10 minutes

a. 5 weeks b. 6 weeks c. 4 mins
f. 5 mins 35 sec
d. 3 weeks 5 days e. 5 weeks 1 day c. 32 months
f. 48 months
4. Convert the following into hours:
c. 96 days
a. 3 days b. 4 days
c. 85 days
d. 4 days 6 hours e. 8 days 7 hours f. 103 days
c. 80 hours
5. Convert the following into minutes: f. 92 hours
c. 95 minutes
a. 5 hours b. 12 hours f. 315 minutes

d. 6 hours 10 minutes e. 3 hours 20 minutes

6. Convert the following into seconds:

a. 3 mins b. 7 mins

d. 9 mins 30 sec e. 6 mins 20 sec

7. Convert the following into years and months:

a. 16 months b. 24 months

d. 28 months e. 40 months

g. 52 months

8. Convert the following into months and days:

a. 60 days b. 80 days

d. 100 days e. 125 days

9. Convert the following into weeks and days:

a. 65 days b. 17 days

d. 92 days e. 100 days

10. Convert the following into days and hours:

a. 48 hours b. 50 hours

d. 100 hours e. 120 hours

11. Convert the following into hours and minutes:

a. 120 minutes b. 85 minutes

d. 245 minutes e. 310 minutes

Oasis School Mathematics Book-4 173

12. Convert the following into minutes and seconds:

a. 90 seconds b. 120 seconds c. 150 seconds
f. 150 seconds
d. 195 seconds e. 220 seconds

Answers:
1. a. 24 months b. 29 months c. 36 months d. 39 months e. 50 months
f. 67 months 2. a. 90 days b. 75 days c. 110 days d. 136 days e. 157 days
3. a. 35 days b. 42 days c. 17 days d. 26 days e. 36 days
4. a. 72 hrs b. 96 hrs c. 58 hrs d. 102 hrs e. 199 hrs f. 219 hrs
5. a. 300 mins b. 720 mins c. 315 mins d. 370 mins e. 200 mins
f. 250 mins g. 395 mins 6. a. 180 sec b. 420 sec c. 240 sec d. 570 sec
e. 380 sec f. 335 sec 7. a. 1 yr 4 months b. 2 yrs c. 2 yrs 8 months
d. 2 yrs 4 months e. 3 yrs 4 months f. 4 yrs g. 4 yrs 4 months
8. a. 2 months b. 2 months 20 days c. 3 months 6 days d. 3 months 10 days
e. 4 months 5 days 9. a. 9 weeks 2 days b. 2 weeks 3 days c. 12 weeks 1 day
d. 13 weeks 1 day e. 14 weks 2 days f. 14 weeks 5 days
10. a. 2 days b. 2 days 2 hrs c. 3 days 8 hrs d. 4 days 4 hrs e. 5 days f. 3 days 20 hrs.
11. a. 2 hrs b. 1 hr 25 mins c. 1 hr 35 mins d. 4 hrs 5 mins e. 5 hrs 10 mins f. 5 hrs. 15 mins.
12. a. 1 min 30 sec b. 2 mins c. 2 mins 30 sec d. 3 min 15 sec e. 3 mins 40 sec f. 2 mins. 30 sec.

Addition and subtraction of time
Basic preparation for addition of time with carry over:

45 mins + 35 mins = 80 mins = 1 hr. 20 mins My logic !
40 mins + 30 mins = 70 mins = 1 hr. 10 mins 80 minutes
56 mins + 34 mins = 90 mins = ........ hrs ........ mins = 60 minutes + 20 minutes
48 mins + 56 mins = ........ mins = ........ hrs ........ mins = 1 hour 20 minutes
40 sec + 25 sec = 65 sec = 1 min 5 sec
45 sec + 30 sec = ........ sec = ........ min ........ sec
55 sec + 35 sec = ........ sec = ........ min ........ sec

Study the following examples and develop the idea of addition of time.

Example : Add:

Hours Minutes Seconds
15
12 32 25 Add hours, minutes and
40 seconds separately.
+ 6 20

18 52

174 Oasis School Mathematics Book-4

Example :

Hours Minutes Seconds Steps:

• Add seconds : (40 + 25) sec = 65 sec

12 50 40 = 1 min 5 sec. carry over 1 min

+ 6 40 25 • Add minutes : (50 + 40) mins = 90 mins

18 90 65 • Add carry over : (90 mins + 1 mins = 91 mins

18 91 5 = 1 hrs. 31 mins. carry over 1 hrs

19 31 5 • Add hrs. (12 + 6) hrs

• Add carry over : 18 hrs + 1 hr = 19 hrs

Example : Steps:

Months Days Hours • Add hours : 20 hrs + 10 hrs = 30 hrs
8 24 20
+ 6 12 10 30 hrs = 1 day 6 hrs. carry over 1 day
14 36 30
14 37 6 • Add days : (24 + 12) days = 36 days
15 7 6
• Add days with carry over

36 days + 1 day = 37 days

1 month 7 days carry over 1 month

• Add months : (8 + 6) months = 14 months

• Add carry over : 14 + 1 = 15 months

Example :

Year Months Days Steps:

6 10 24 • Add days : 24 days + 18 days = 42 days

= 1 month 12 days, carry over 1 month

+ 9 8 18 • Add months (10 + 8) months = 18 months

15 18 42 • Add months with carry over 18 months + 1

month = 19 months

15 19 12 = 1 yr 7 months. carry over 1 yr.

16 7 12 • Add year : (6 + 9) yrs = 15 yrs

• Add with carry over: 15 yrs + 1 yrs = 16 yrs

Subtraction (with borrowing)

Basic preparation for subtraction with borrowing:

1 hr - 10 mins = = 60 mins – 10 mins = 50 mins

1 day - 6 hrs = 18 hrs = 24 hrs – 6 hrs = 18 hrs

1 min - 15 sec = 45 sec = 60 sec – 15 sec = 45 sec

1 day - 14 hrs = 10 hrs = 24 hrs – 14 hrs = 10 hrs

Oasis School Mathematics Book-4 175

Example :

Hours Minutes Seconds Steps:
24
In seconds 20 < 45
15 25 20 • Borrow 1 min from min leaving 24 mins, now it

- 6 45 45 is 1 min 20 sec = 80 sec, in second column
• Subtract seconds (80 - 45) sec = 35 sec
8 39 35 Again, in minutes 24 < 45
• Borrow 1 hr from 15 hrs leaving 14 hrs, now it
Example :
is 1 hr 24 minutes column
Years Months Days • Subtract minutes : (84 - 45) mins = 39 mins
• In hrs, Subtract hrs : (14 - 6) hrs = 8 hrs
24 8 14
- 11 10 20 Steps:
12 9 24
In days 14 < 20.
• Borrow 1 month from 8 months leaving 7

months, now in days, 1 month 14 days = 44
days
• Subtract days : (44 - 20) days = 24 days
In month 7 < 10
• Borrow 1 year from 24 year leaving 23 years,
now in months, 1 year + 7 months = 19 months
• Subtract months : (19 - 10) months = 9 months
• Subtract years : (23 - 11) years = 12 years

Exercise 7.5

1. Add:

a. Hours Minutes Seconds b. Hours Minutes Seconds
8 14 36
13 45 30 + 6 30 14

+ 12 10 15

c. Months Days Hours d. Years Months Days
4 17 10 8 6 15
+ 6 8 5 + 3 4 12

2. Add: b. Hours Minutes Seconds
a. Hours Minutes Seconds 8 40 42
15 52 35 + 7 52 25
+ 8 12 45

176 Oasis School Mathematics Book-4

c. Months Days Hours d. Months Days Hours
8 26 6 3 25 20
+ 4 24 4 + 2 20 8

e. Hours Minutes Seconds f. Years Months Days
6 22 18
+ 3 26 19 9 8 12

+ 5 9 24

3. Subtract::

a. Hours Minutes Seconds b. Hours Minutes Seconds
21 12 28
16 15 24 - 12 50 40

- 8 50 35

c. Weeks Days Hours d. Weeks Days Hours
8 12
10 2 12 13 3 20

- 2 6 - 7 6

e. Months Days Hours f. Months Days Hours
8 12 10
- 3 18 16 11 12 9

- 3 20 16

Consult your teacher.

Verbal problems related to time

Look at this example,
School starts at 8 : 30 A.M. and closes at
3.00 P.M. How long is the school open for ?
School remains open from 8 : 30 A.M. to
3:00 P.M.
Time from 8:30 A.M. to 9 A.M. = 30 minutes
Time from 9 A.M. to 3.00 P.M = 6 hours
\ School is open for 6 hours 30 minutes.
Look at one more example,
Asmi is 10 years 10 months and 10 days old.
Her sister is 12 years 11 months and 12 days old .What is the age difference
between the two sisters?

Oasis School Mathematics Book-4 177

Their age difference is

(12 years 11 months 12 days) - (10 years 10 months 10 days)

Years Months Days
12
12 11 10
2
- 10 10

2 1

\ Their age difference is 2 years 1 months 2 days.

Exercise 7.6

1. a. Calculate the number of days between 13th Bhadra to 29 th Bhadra.
b. Calculate the number of hours between 5 A.M. to 8 P.M.
c. Calculate the number of years from 2068 B.S to 2073 B.S.

2. a. Find the sum of 3 hours 30 minutes 50 seconds and 5 hours 40 minutes 35
seconds.

b. Find the sum of 6 months 13 days 20 hours and 3 months 24 days 10 hours.
3. a. Find the difference between 3 hours 20 minutes 15 seconds and 3 hours 50

minutes 25 seconds.
b. Find the difference between 12 years 4 months 13 days and 6 years 6

months 20 days.
4. a. Anusuya's exams begin at 17th Shrawan and get over on 29th. How many

days are her exam continue?
b. Pragik started his journey at 7.30 A.M. He completed it at 2.45 P.M. Find

the duration of his journey.
5. a. A boy was born on Shrawan 12, 2050. How old was he on Shrawan 12,

2057?
b. A bus takes 3 hours 20 minutes to reach Mungling from Kathmandu and

2 hours 30 minutes from Mungling to Pokhara. How long does it take to
reach Pokhara from Kathmandu.?
c. Gyaljen is 15 years 6 months 12 days old and Bikash is 12 years 8 months
20 days old. By how many years is Gyaljen older than Bikash?
6. a. Prayag started his journey from Kathmandu at 7 : 30 A.M. He reached
Nepalgunj at 8 : 45 P.M. Find the duration of his journey.
b. A bus takes 4 hours 40 minutes from Gorkha to Pokhara if it leaves at 8 :
30 A.M. from Gorkha. What is the arrival time of the bus in Pokhara?

Consult your teacher.

178 Oasis School Mathematics Book-4

Worksheet

See the calendar of this year and write the date of the following.

Date
• Republic Day. 15th Jestha

• Democracy Day ..........................................

• Deepawali ..........................................

• Teacher's Day ..........................................

• Bhanu Jayanti ..........................................

• Children's Day ..........................................

• Women's Day ..........................................

• Vijaya Dashami ..........................................

• World Environment Day ..........................................

• Udhauli Festival ..........................................

• Tamu Lhosar ..........................................

• Indra Jatra ..........................................

• Sonam Lhosar ..........................................

• Chritsmas ..........................................

• Buddha Jayanti ..........................................

• Martyr's Day ..........................................

• Your result of final examination ..........................................

Oasis School Mathematics Book-4 179

Project

Paste photographs of your family members with their date of birth in short form.

Grandfather Grandmother

Photo Photo

Date of birth Date of birth
Father Mother
Photo Photo

Date of birth Brother Date of birth
Sister Photo Me
Photo
Photo

Date of birth Date of birth Date of birth

Their present age in year

Grandfather = years
years
Grandmother = years
years
Father = years
years
Mother = years

Sister =

Brother =

Yourself =

180 Oasis School Mathematics Book-4

Objective Questions

1. Minute hand of a clock is at 4 and hour hand is between 2 and 3,
then the time is

2 : 30 2 : 20 2 : 40

2. The short form of the date 13th Bhadra 2071:

2071/05/13 2071/13/05 05/13/2071

3. The number of days in a leap year is

364 days 366 days 365 days

4. 50 months is equal to 4 years 1 4 years 2
month months
2 years 2
months

5. Time between 5 A.M. to 10 P.M. is

5 hours 17 hours 6 hours

6. A girl was born on 12th Shrawn 2064. What was her age on 12th
Bhadra 2070?

6 years 1 month 6 years 5 years 1 month

7. 135 minutes is equal to:

1 hr 15 mins 2 hr 15 mins 2 hr 45 mins

Number of correct answers

Oasis School Mathematics Book-4 181

Unit Test Full marks -20

1. Write the time in A.M. or P.M. 2
a. 8. o' clock in the morning. 2
b. 2 : 30 in the afternoon. 6×1=6

2. Write the date in short form.
a. 2071 Bhadra 13
b. 13th February 1980

3. Convert the following as indicated.
a. 15 months into year.
b. 2 years 6 months into months.
c. 80 minutes into hours and minutes.
d. 2 hours 25 minutes into minutes.
e. 65 days into months and days.
f. 2 months 15 days into days.

4. Add: 4

a. Hrs Mins Sec b. Years Months Days
3 28 25
+ 5 42 40 14 9 20

+ 12 6 15

5. Subtract. 4

a. Hours Minutes Second b. Years Months Days
16 45 50
– 7 36 25 18 3 12

– 6 7 25

6. A bus takes 5 hours 50 minutes to reach Pokhara from Kathmandu

and 2 hours 15 minutes from Pokhara to Kusma. How long does it

take to reach Kusma from Kathmandu? 2

182 Oasis School Mathematics Book-4

UNIT

8 Money Matters

12 Estimated Teaching Hours: 15
93

6

Contents • Conversion of money
• Addition and subtraction of money

Expected Learning Outcomes

Upon completion of the unit, students will be
able to develop the following competencies:

• To convert paise into rupees and rupees into paise
• To add and subtract money

Materials Required: Nepali coins, Nepali notes
Oasis School Mathematics Book-4 183

Our coins:
Our paper notes:

Class Assignment b.

Count the given Nepali notes: = Rs.............
a.

= Rs.............

c.

= Rs.............

Conversion of money

To convert money from Paise to Rupees or Rupees to Paise, we use the
relation

Example 1: Re 1 = 100 Paise

Convert the following Rs. into paise. I understand, to convert
Rs. into paise, I have to
a. Rs. 2 b. Rs. 5 c. Rs. 6
multiply Rs. by 100

Solution:

a. Rs. 2 = 2 × 100 Paise Re. 1 = 100 Paise
= 200 Paise Rs. 2 = 2 × 100 Paise
b. Rs. 5 = 5 × 100 Paise

= 500 Paise

c. Rs. 6 = 6 × 100 Paise

= 600 Paise

184 Oasis School Mathematics Book-4

Example 2: I understand, to convert Paise
Convert the following Paise into Rupees (Rs). into Rupees, I have to divide
Solution:
Paise by 100.

a. 500 Paise b. 200 Paise c. 30 Paise d. 8 Paise

= Rs 500 = Rs 210000 = Rs 30 = Rs 8
100 = Rs 2 100 100

= Rs 5 = Rs 0.3 = Rs 0.08

Example 3:

Convert Rs 5 and 60 Paise into Paise. Re 1 = 100 Paise
Rs 5 = 5 × 100 Paise
Solution:
Rs 5 and 60 Paise
= 5 × 100 Paise + 60 Paise

= 500 Paise + 60 Paise
= 560 Paise
Example 4:

Convert Rs 8 and 30 Paise into Rupees.

Solution: 1 P = Rs 1
100
Rs 8 and 30 Paise

= Rs 8 + Rs 30 30 P = Rs 30
100 100

= Rs 8 + Rs 0.30

= Rs 8.3
Example 5:

Convert 560 Paise into Rupees and Paise Rs

Solution: Paise

560 Paise

= Rs. 560
100

= Rs. 5 and 60 Paise

Quotient = Rs.
Reminder = Paise

Rs 5.80 = Rs 5 and 80 Paise
Rs 3.70 = Rs 3 and 70 Paise
Rs 4.15 = Rs 4 and 15 Paise

Oasis School Mathematics Book-4 185

Addition and subtraction of money

Study the given examples properly and get the idea of addition and
subtraction of money:

Example 6: Steps:

Add: • Add Paise : (65 + 55 ) P = 120 Paise
Rs Paise
25 65 120 Paise = Re 1 and 20 Paise, write 20 Paise in
the column of Paise, carry over Re 1

+ 15 55 • Add Rs. 25 + 15 = Rs. 40
40 120 • Add with carry over Rs. 40 + Re 1 = Rs. 41

41 20

Rs. 41.20 = Rs 41 and 20 Paise.

Alternative method Steps:

Rs Paise • Convert Rs. 25 and 65 Paise into Rs.

25 65 = Rs 25.65 Rs. 25 + Rs. 65 = Rs. 25 + Rs. 0.65 = Rs. 25.65
100
+ 15 55 = + Rs 15.55
• Convert Rs. 15 and 55 Paise into Rs.
Rs 41.20
Rs 15 and 55 Paise = Rs 15.55

Rs. 41.20 = Rs 41 and 20 Paise. • Add Rs as the addition of decimal number.

Example 7: Steps:

Subtract: In Paise, 20 < 80
Rs Paise
35 20 • Borrow Re 1 from Rs. 35, leaving Rs. 34 in Rs.
– 21 80 column. Now, Re 1 and 20 Paise = 120 Paise
13 40
• Subtract Paise : 120p - 80p = 40p
Rs. 13.40 paise
• Subtract Rs.

Rs (34 - 21) = Rs 13

Alternative method Steps:

Rs Paise • Convert Rs. 35 and 20 Paise into Rs.

35 20 = Rs 35.20 Rs. 35 + Rs 20 = Rs. 35 + Rs. 0.20 = Rs. 35.20
100
– 21 80 = – Rs 21.80
• Convert Rs. 21 and 80 Paise into Rs.
Rs 13.40
Rs. 21 and 80 Paise = Rs. 21.80
Rs. 13.40 = Rs 13 and 40 paise.
• Subtract Rs. as in the subtraction of decimal
numbers.

186 Oasis School Mathematics Book-4

Exercise 8.1

1. Convert the following into Paise:

a. Rs. 5 b. Rs. 8 c. Rs. 12

d. Rs. 4 and 20 Paise e. Rs. 6 and 35 Paise f. Rs. 12 and 70 Paise

g. Rs. 25 and 15 Paise h. Rs. 10 and 50 Paise i. Rs. 12 and 5 Paise

j. Rs. 15 and 5 Paise

2. Convert the following into Rupees.

a. 50 Paise b. 80 Paise c. 5 Paise

d. Rs. 2 and 30 Paise e. Rs. 13 and 50 Paise f. Rs. 15 and 40 Paise

g. Rs. 15 and 24 Paise h. Rs. 25 and 12 Paise

i. Rs. 60 and 5 Paise j. Rs. 35 and 35 Paise

3. Convert the following Paise into Rupees and Paise.

a. 120 Paise b. 360 Paise c. 520 Paise

d. 340 pasie e. 450 Paise f. 380 Paise

4. Add: b. Rs. Paise c. Rs. Paise
26 90 252 75
a. Rs. Paise + 13 40 + 114 60
15 80
+ 12 60

d. Rs. Paise e. f.
148 35 Rs. 46.85 Rs. 63.76
+ 112 95 + Rs. 13.35 + Rs. 20.74

g. Rs. 76.84 h. Rs. 152.15 i. Rs. 227.84
+ Rs. 13.93 + Rs. 156.95 + Rs. 118.63

Oasis School Mathematics Book-4 187

5. Subtract: b. Rs. Paise c. Rs. Paise
a. Rs. Paise 27 50 182 35
58 25 - 14 80 - 160 85
- 36 75
e. f.
d. Rs. Paise Rs. 45.26 Rs. 84.38
246 32 - Rs. 23.85 - Rs. 38.63
- 135 85

g. Rs. 182.35 h. Rs. 246.25 i. Rs. 193.56
- Rs. 148.57 - Rs. 132.85 - Rs. 46.84

6. Add or subtract: b. Rs. 86.34 + Rs. 98.17
a. Rs. 18.46 + Rs. 93.32

c. Rs. 132.92 + Rs. 223.84 d. Rs. 45.63 + Rs. 56.84 + Rs. 73.86

e. Rs. 123.56 + Rs. 132.84 + Rs. 259394 f. Rs. 86.32 - Rs. 68.47

g. Rs. 92.84 - Rs. 78.96 h. Rs. 146.52 - Rs. 118.76

i. Rs. 256.12 - Rs. 187.36

7. a. A boy has Rs. 35 and 85P. Convert all his money into Paise.

b. Ankur had Rs 43.84, his father gave him Rs. 32.46. How much money
does he have now?

c. Cost of sugar is Rs. 48 and 25 Paise per kg and cost of salt is Rs. 25 and 85
Paise per kg. What is the cost of 1 kg sugar and 1kg salt?

d. A boy had Rs. 43.85. He bought a copy for Rs. 12.90. How much money is
left with him?

Consult your teacher.

188 Oasis School Mathematics Book-4

Worksheet

Rupsha, Prokmi, Arpan and Mokshata went in food festival.

Food Menu

Mo:Mo Dosa Samosa Rasmalai

Rs 50.50 Rs 75.35 Rs 20.50 Rs 30.25

Rupsha orderd one plate MoMo and a Samosa.
Prokmi ordered one plate Dosa and Rasmalai
Arpan orderd one plate samosa and Rasmalai
Mokshata orderd one plate MoMo and one plate Dosa

How much each has to pay?

Rupsha Prokmi Mokshata Arpan

Oasis School Mathematics Book-4 189

Objective Questions

Colour the correct alternatives:

1. 1560 paise is euql to

Re. 1 and 56 P Rs. 15 and 60 P Rs. 156
Rs. 436 and 50 P
2. Rs 43.65 is equal to Rs. 4 and 36 P
Rs. 43 and 65 P

3. Rs 25.60 + Rs 20 and 80 P is equal to

Rs. 46 and 40 P Rs. 45 and 20 P Rs. 46 and 20 P

4. 3675 paise is not equal to Rs. 36.75 Rs. 367 and 5 P
Rs. 36 and 75 P Rs. 24.75

5. Rs 45.25 – Rs 20 and 75 P is equal to

Rs. 24.50 Rs. 25.50

6. 365 P + Rs 23.25 P + Rs 15.10 is equal to

Rs. 41 Rs. 41 and 20 P Rs. 42

7. Which of the following relation is not ture?

Re. 1 = 100 P 2 P = Rs. 200 1 P = Rs. 1
100

Number of correct answers
190 Oasis School Mathematics Book-4

Unit Test Full marks -20

1. Convert into Paise. b. Rs. 5.65 2
a. Rs. 16 and 60 P 2
b. Rs. 24.65 2×2=4
2. Convert into Rs and Paise.
a. 3625 Paise b. Rs. Paise 2×2=4
130 90
3. Add: + 104 20
a. Rs. Paise
85 75 b. Rs. Paise
+ 125 55 214 15
- 158 85
4. Subtract:
a. Rs. Paise
85 25
- 62 75

5. Simplify: 2×2=4
a. Rs. 20 and 80 P + Rs. 175 and 25 P – Rs. 65 and 20 P

b. Rs. 125.65 – Rs. 75.80 + Rs. 65 and 30 P

6. Solve the following problems. 4

a. Aman has Rs. 85 and 60 P, his father gave him Rs. 250 and 80 P.
How much money does he have now?

b. Dawa had Rs. 125.60. He bought a book for Rs. 75 and 80 P. How
much money does he have now?

Oasis School Mathematics Book-4 191

UNIT

9 Metric
Measurement

12 Estimated Teaching Hours: 15
93

6

Contents • Units of measurement of length, weight
and capacity

• Conversion of unit of length, weight and
capacity

• Addition and subtraction of length, weight
and capacity.

Expected Learning Outcomes

Upon completion of the unit, students will be
able to develop the following competencies:

• To know the different units of measurement.
• To convert the unit of length, weight and capacity into another

unit.
• To add and subtract the length, weight and capacity.

Materials Required : Ruler, measuring tape, pan balance, spring balance, etc.

192 Oasis School Mathematics Book-4

Measurement of length

We have already learnt about the units of measuring length in the previous
class.

Lengths are measured in kilometres (km), metres (m), centimetres (cm),

millimetres (mm), etc. Km, m, cm and mm

Shorter objects are measured in cm or mm. are used to measure
length.

Longer objects are measured in m or km.

Length of an object is measured by measuring tape, ruler, etc.

Let’s guess about units Length of the classroom
for measuring the length is measured in metre (m).

of following objects.

a. Length of a classroom

b. Length of a pencil Length of a pencil is
measured in cm.

c. Length of a book

Length of a book is
measured in cm.

d. Length of a bench Length of a bench is
measured in metre

(m).

Oasis School Mathematics Book-4 193

Conversion of unit of length

To convert one unit of length into another, let's remember;

10 mm = 1 cm To convert cm
100 cm = 1 m into mm I have to
1000 m = 1 km multiply cm by 10.

Example 1: Multiply m by 100 to
convert into cm.
Convert 5 cm into mm.
Solution:
5 cm = 5 × 10 mm
= 50mm

Example 2:

Convert 4 m into cm.
Solution:
4m = 4 × 100 cm
= 400 cm

Example 3: 1 cm = 10 mm
6 cm = 6 × 10 mm
Convert 6 cm 5mm into mm.
Solution:
6 cm 5mm
= 6 × 10 mm + 5 mm
= 60 m + 5 mm
= 65 mm

Example 4: I have to divide cm
by 100 to convert into
Convert 5 m 16 cm into cm.
metre.

Solution:

= 5 × 100 cm + 16 cm 1 m = 100 cm
= 500 cm + 16 cm 5 m = 5 × 100 cm
= 516 cm

194 Oasis School Mathematics Book-4

Example 5: Example 6:

Convert 6 mm into cm. Convert 25 cm into m.

Solution: 10 mm = 1 cm Solution: 100 cm = 1 m

6 mm = 6 cm 1 mmmm ==110160 cm 25 cm = 25 m 1 cm = 1 m
10 6 cm 100 100
25
= 0.6 cm = 0.25 m 25 cm = 100 m

Example 7: Example 8:

Convert 5m 30 cm into m. Convert 15 cm 6 mm into cm.

Solution: 30 3 Solution: 6 = 0.6
100 10 10
5 m 30 cm = 15 cm 6 mm

= 5m + 30 m = 0.3 = 15 cm + 6 cm
100 10

= 5m + 0.3 m = 15 cm + 0.6 cm

= 5.3 m = 15.6 cm

Example 9:

Convert 6 km 550 m into metre.

Solution: 1 km = 1000 m
6 km = 6 × 1000 m
6 km + 550 m = 6000 m

= 6 × 1000 m + 550 m

= 6000 m + 550 m

= 6550 m

Example 10: Example 11:

Convert 5 km 600 m into km. Convert 57 mm into cm and mm.

Solution: Solution: 57
10
5 km 600 m = 5 km + 600 km 57 mm = cm
1000
=
= 5 km + 6 km 5 cm 7 mm
10
10 ) 57 ( 5 cm Quotient
= 5 km + 0.6 km - 50 cm
mm
= 5.6 km 7 mm Remainder

Example 12:

Convert 3160 m into km and m.

Solution: 1000 ) 3160 ( 3 km
- 3000
3160 m = 3160 km 160 m
1000
Oasis School Mathematics Book-4 195
= 3 km 160 m

Exercise 9.1

1. Which is the appropriate unit (mm, cm, m or km) to measure the

following objects?

a. length of your book b. length of a blackboard

c. length of your classroom d. height of a person

e. distance between two places f. thickness of your Maths book

2. Convert into millimetre (mm).

a. 2 cm b. 2 cm 5 mm c. 3 cm 6 mm

d. 4 cm 2mm e. 12 cm 7 mm f. 20 cm 3 mm

3. Convert into centimetre (cm).

a. 4 m b. 4m 15 cm c. 6 m 20 cm

d. 15 m 80 cm e. 10 m 90 cm f. 16 m 25 cm
c. 4 km 550 m
4. Convert into metre (m).

a. 3 km b. 2 km 315 m

d. 6 km 600 m e. 8 km 850 m f. 12 km 750 m

5. Convert into cm. b. 30 mm c. 56 mm d. 75 mm e. 94 mm
a. 5 mm

6. Convert into m. b. 325 cm c. 640 cm d. 720 cm e. 1240 cm
a. 500 cm

7. Convert into km.
a. 2000 m b. 4326 m c. 7645 m d. 6500 m e. 12425 m

8. Convert into cm and mm.

a. 45 mm b. 56 mm c. 74 mm d. 85 mm

9. Convert into m and cm.

a. 250 cm b. 475 cm c. 880 cm d. 1240 cm

10. Convert into km and m.

a. 3420 m b. 4746 m c. 7500 m d. 16324 m

Answers:

1. Consult your teacher 2. a. 20 mm b. 25 mm c. 36 mm d. 42 mm
c. 620 cm d. 1580 cm
e. 127 mm f. 203 mm 3. a. 400 cm b. 415 cm c. 4550 m d. 6600 m
c. 5.6cm d. 7.5 cm
e. 1090 cm f. 1625 cm 4. a. 3000 m b. 2315 m d. 7.20 m e. 12.40 m
e. 12.425 km 8.a. 4cm 5mm
e. 8850 m f. 1275 m 5. a. 0.5cm b. 3 cm b. 4m 75 cm c. 8m 80 cm
d. 16 km 324 m
e. 9.4 cm 6. a. 5m b. 3.25m c. 6.40 m

7. a. 2 km b. 4.326 km c. 7.645 km d. 6.5 km

b. 5cm 6mm c. 7cm 4 mm d. 8cm 5mm 9. a. 2m 50cm

d. 12m 40 cm 10. a . 3km 420 m b. 4 km 746 cm c. 7km 500 m

196 Oasis School Mathematics Book-4

Quick method of conversion. 1 2 7 5 cm

1 2 0 cm

1m 20 cm 12 m 7 cm

Class Assignment Convert into km and m.

Convert into m and cm. 1275 m = 1 km 275 m
1550 m = ...............................
120 cm = 1 m 20 cm 1765 m = ...............................
156 cm = ............................... 2500 m = ...............................
225 cm = ............................... 2760 m = ...............................
335 cm = ............................... 1440 m = ...............................
180 cm = ............................... 2320 m = ...............................
195 cm = ...............................
158 cm = ............................... 1km 250 m

1 m 35 cm 1250m
135
Convert into m.
Convert into cm.
1 km 250 m = 1250 m
1m 35 cm = 135 cm 1 km 300 m = ...............................
1 m 48 cm = ............................... 1 km 70 m = ...............................
1 m 60 cm = ............................... 1 km 85 m = ...............................
1 m 95 cm = ............................... 1 km 240 m = ...............................
1 m 86 cm = ............................... 2 km 280 m = ...............................
2 m 7 cm = ............................... 3 km 50 m = ...............................
3 m 5 cm = ...............................

Oasis School Mathematics Book-4 197

Addition and subtraction of length

Addition and subtraction of length.

Study the given examples carefully and get the idea of addition and subtraction

of length. Steps:
Example 1:

Add: m cm • Add cm : (85 + 75) cm = 160 cm
km 450 85 = 1 m 60 cm, carry over 1 m
5 720 75 • Add m: (450 + 720) m = 1170 m
+ 2 1170 160 Add with carry over 1, (1170 + 1) m = 1171 m
7 1171 60 = 1 km 171 m, carry over 1 km
7 171 60 • Add km: 5 + 2 = 7 km
8 Add carry over : (7 + 1) km = 8 km

I got a quick idea!

160 cm last two digits represent cm

1 m 60 cm Remaining digit m
1171 m last three digits represent m

1 km 171m Remaining digit km

Example 2: cm mm Steps:
Add: 85 8
m 82 6 • Add mm: 8 + 6 = 14 mm
15 167 14 = 1 cm 4 mm, carry over 1 cm
+ 26 168 4 • Add cm: 85 + 82 = 167 cm
41 68 4 Add cm with carry over 167 cm + 1 cm
41 = 168 cm
42 m 1 m cm = 1 m 68 cm, carry over 1 m
• Add m : (15 + 26) m = 41 m
Example 3: 350 25 Add carry over : (41 + 1) m = 42m
Subtract: 670 85
km 1 km 679 40 Steps:

6 In cm,
- 3 • 25 < 85
2 • Borrow 1 m from 350 leaving 349 m, now 1

m 25 cm = 125 cm. Subtract cm: ( 125 - 85)
cm = 40 cm
In m,
• 349 < 670.
• Borrow 1 km from 6 km leaving 5 km, now
1 km 349 m = 1349 m
• Subtract m: 1349 m - 670 m = 679 m
• Subtract km: (5 - 3) km = 2 km

198 Oasis School Mathematics Book-4

Example 4: cm 1 cm mm Steps:
Subtract:
m 1 m 25 3 In mm,
68 7 • 3 < 7.
18 56 6 • Borrow 1 cm from 25 cm leaving 24 cm.
- 10
7 Now, 1 cm 3 mm = 13 mm.
• Subtract mm: (13 - 7) mm = 6 mm
In cm,
• 24 < 68.
• Borrow 1 m, from 18 m leaving 17 m, now

1 m 24 cm = 124 cm
• Subtract cm: (124 - 68) cm = 56 cm
• Subtract m: (17 - 10) m = 7m

Exercise 9.2 b. km m c. km m
17 830 12 620
1. Add: + 12 650 + 11 740
a. km m
5 350
+ 7 840

d. m cm e. m cm f. m cm
84 63 123 62 224 68
+ 73 54 + 184 76 + 123 53

g. cm mm h. cm mm i. km m cm
23 8 52 9 18 644 92
+ 54 6 + 25 3 + 15 528 18

j. km m cm k. km m cm
27 913 95 45 886 76
+ 12 89 6 + 23 523 84

l. m cm mm m. m cm mm
86 84 9 92 78 6
+ 72 18 5 + 13 53 9

Oasis School Mathematics Book-4 199

2. Subtract: b. km m c. m cm
a. km m 126 362 65 36
52 720 - 68 473 - 48 45
- 23 856

d. m cm e. cm mm f. cm mm
256 42 15 6 16 3
- 133 68 - 7 8 - 5 9

g. km m cm h. km m cm
76 410 57 95 286 12
- 12 650 78 - 12 570 48

i. m cm mm j. m cm mm
25 45 3 116 24 7
- 12 75 8 - 112 74 9

3. Add or subtract:

a. 5 km 360 m 65 cm + 7 km 810 m 58 cm
b. 3 km 210 m 20 cm - 1 km 740 m 80 cm
c. 85 m 35 cm 5 mm + 70 m 34 cm 8 mm
d. 212 m 15 cm 3 mm - 124 m 42 cm 7 mm

4. In the given figure find the distance of the following:

Gate 35 m 8 cm

Playground

a. School to the playground and the hostel Consult your teacher.
b. Hostel to the garden and the gate
c. Gate to the playground and the school
d. Gate to the school and the hostel

200 Oasis School Mathematics Book-4