Primary 4

Boost! Math

Name Working Backwards (Lesson 16)

Tutor Working Backwards (Lesson 16)

Topic

Primary 4: Boost! Math

1. Nemo multiplies his age by 7, adds 15 and then subtracts 26 from it. His answer is

31 years. How old is he now?

Ans:

2. Bus 88 left the bus terminal with some passengers.

At the first stop, 14 passengers got on and 8 passengers got off.

At the second stop, 5 passengers got on and 13 passengers got off.

At the third bus stop, 22 passengers got on and 14 passengers got off.

At the fourth stop, all 53 passengers alighted the bus.

How many passengers were on the bus at first?

Ans: 1

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Primary 4: Boost! Math

3. There were some eggs in a basket. Peter took half of the eggs out and then put 3

egg back into the basket. He repeated this process. There were 24 eggs left in the

basket in the end. How many eggs were there in the basket at first?

Ans:

4. Tania and Jack had 50 game cards altogether. They played 2 games.

In the first game, Tania lost 10 cards to Jack.

In the second game, Jack lost 7 cards to Tania.

In the end, both of them had the same number of cards.

How many cards did each of them have at first?

Ans: Tania: and Jack:

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Primary 4: Boost! Math

5. Henry had some gold coins. He spent 21of his gold coins on a magic wand. He then

spent 1 of the remainder on a bottle of magic potion. If he had 152 gold coins left,

3

how many gold coins did Henry have at first?

Ans:

6. There were 45 apricots in boxes X, Y and Z. If 7 apricots were moved from box X to

box Y,10 apricots were moved from box Y to box Z and 12 apricots were moved

from box Z to box X, the number of apricots in all 3 boxes will be the same.

How many apricots are there in each of the boxes at first?

Ans: Box X: , Box Y: and Box Z: 3

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Primary 4: Boost! Math

7. A number is added to 13. The sum is then multiplied by 3.

The product is divided by 8.

9 is then subtracted from the quotient and the answer is 3. What is the number?

Ans:

8. May bought some buttons. She used half of them and an additional 4 buttons to sew

on a dress. She used half of the remainder and another 2 buttons to sew on some

cushions. She had 27 buttons left. How many buttons did May buy?

Ans: 4

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Primary 4: Boost! Math

9. Robin took the train to his grandmother's house. He boarded the train at StationA.

At Station B, 29 passengers alighted and 37 people boarded the train.

At Station C, 38 passengers alighted and 15 people boarded the train.

Robin and 19 other passengers alighted at Station D.

When the train left station D, there were 63 passengers on the train.

How many passengers were on the bus when Robin boarded the train?

Ans:

10. Ron owns a fruit shop. He sold 1 of the fruits in the morning. He sold 2 of the

45

remaining fruits in the afternoon. He was then left with 324 fruits. How many fruits

did Ron have at first?

Ans: 5

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Primary 4: Boost! Math

11. Joe, Keith and Lucas had 186 stickers at first.

Joe gave 16 stickers to Keith. Keith gave 31 stickers to Lucas and Lucas gave 23

stickers to Joe. The three boys had the same number of stickers in the end.

(a) How many stickers did Joe have at first?

(b) How many stickers did Keith have at first?

(c) How many stickers did Lucas have at first?

Ans (a) 6

(b)

(b)

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Primary 4: Boost! Math

12. Jugs A and B contain 700 ml of juice altogether.

245 ml of juice was poured from jugA to jug B.

Then 165 ml of juice was poured from jug B to jugA.

Both the jugs have an equal amount of juice in the end.

(a) How much juice was there in jugA at first?

(b) How much juice was there in jug B at first?

Ans (a) 7

(b)

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