Multiplying, dividing and mixed operations · Ages 9–10

Estimate first, then check worksheet

Part of: Multiplying and dividing by two digits; divisibility

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Multiplying, dividing and mixed operations · Ages 9–10

Numsprite
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Name:Date:Score:／48

Write each answer in the space. For word problems, show your working and write a sentence answer.

1.Estimate 78 × 66: round both to the nearest ten, and the answer is about .
Answer:
2.Without working out the answer: how many digits does 563 × 93 have?
Answer:
3.Without working out the answer: how many digits does 161 × 77 have?
Answer:
4.Estimate 668 × 71 (the three-digit number to the nearest hundred, the two-digit one to the nearest ten): 668 is about , 71 is about , and the answer is about .
Fill in each blank
Answer:
5.Estimate 817 × 71 (the three-digit number to the nearest hundred, the two-digit one to the nearest ten): 817 is about , 71 is about , and the answer is about .
Fill in each blank
Answer:

6.Without working it out, which is 74 × 59 closest to?
- A. 130
- B. 4200
- C. 420
- D. 42000
Choose the right answer
Answer:
7.Without working it out, which is 24 × 68 closest to?
- A. 90
- B. 1400
- C. 140
- D. 14000
Choose the right answer
Answer:
8.Ka-yee works out 962 × 25 and gets 24050. Judging by an estimate, this answer is sensible.
True or false?
Answer:
9.Without working it out, which is 4232 ÷ 46 closest to?
- A. 9
- B. 9000
- C. 900
- D. 90
Choose the right answer
Answer:
10.Ka-yan works out 524 × 69 and gets 36156. Judging by an estimate, this answer is sensible.
True or false?
Answer:
11.Without working it out, which is 5822 ÷ 82 closest to?
- A. 700
- B. 7000
- C. 7
- D. 70
Choose the right answer
Answer:
12.Of these four, which answer must be wrong?
- A. 24 × 47 = 1128
- B. 14 × 28 = 392
- C. 18 × 36 = 6480
- D. 57 × 74 = 4218
Choose the right answer
Answer:

13.Ka-lok has $2,200 and wants to buy 36 ballpoint pens at $59 each. Does Ka-lok have enough money?
- A. You can't tell without working it out exactly
- B. Yes, enough
- C. Exactly, with nothing left
- D. No, not enough
Choose the right answer
Working:
Answer:
14.A charity shares 1226 mooncakes equally among 26 elderly homes. Rounding 1226 to the nearest hundred and 26 to the nearest ten, about how many mooncakes does each home get?
Working:
Answer:
15.Tsz-hin buys 38 water bottles for a charity sale at $68 each. The till shows $25,840. Without working it out, what can you say about this amount?
- A. It is sensible
- B. It is too big
- C. You can't tell without working it out
- D. It is too small
Choose the right answer
Working:
Answer:
16.A cha chaan teng's lunch set is $43, and 29 were sold today. Rounding both numbers to the nearest ten, about how many dollars did the lunch sets take today?
Working:
Answer:
17.An MTR train has 8 cars, and each car can carry up to 293 people. Rounding each car's number to the nearest hundred, about how many people can a train carry at most?
Working:
Answer:
18.Ka-yan has $900 and wants to buy 15 storybooks at $51 each. Does Ka-yan have enough money?
- A. Exactly, with nothing left
- B. You can't tell without working it out exactly
- C. Yes, enough
- D. No, not enough
Choose the right answer
Working:
Answer:

Show the answers and working

Estimate first, then check worksheet: Answers and working

1. 5600
Round 78 and 66 to the nearest ten first, then multiply the two whole tens.
78 is about 80 and 66 about 70: 80 × 70 = 5600.
2. 5
Round 563 to the nearest hundred and 93 to the nearest ten, multiply, then count the digits.
Estimate: 563 is about 600 and 93 about 90, 600 × 90 = 54000, which has 5 digits; the real answer 52359 has 5 too.
3. 5
Round 161 to the nearest hundred and 77 to the nearest ten, multiply, then count the digits.
Estimate: 161 is about 200 and 77 about 80, 200 × 80 = 16000, which has 5 digits; the real answer 12397 has 5 too.
4. 700, 70, 49000
For 668, the tens digit decides the hundred; for 71, the ones digit decides the ten. Then multiply.
668 to the nearest hundred is 700, 71 to the nearest ten is 70: 700 × 70 = 49000.
5. 800, 70, 56000
For 817, the tens digit decides the hundred; for 71, the ones digit decides the ten. Then multiply.
817 to the nearest hundred is 800, 71 to the nearest ten is 70: 800 × 70 = 56000.

6. B. 4200
Round 74 and 59 to the nearest ten and multiply, then see which choice is nearest.
74 is about 70 and 59 about 60: 70 × 60 = 4200.
7. B. 1400
Round 24 and 68 to the nearest ten and multiply, then see which choice is nearest.
24 is about 20 and 68 about 70: 20 × 70 = 1400.
8. True
Round 962 to the nearest hundred and 25 to the nearest ten, estimate, then compare with 24050.
Estimate: 962 is about 1000 and 25 about 30, 1000 × 30 = 30000, so the answer should be near 30000; it is 24050.
9. D. 90
Estimate by multiplying: 46 times roughly what comes close to 4232?
Estimate by multiplying: 46 × 90 is the nearest to 4232, so the answer is about 90 (it is 92).
10. True
Round 524 to the nearest hundred and 69 to the nearest ten, estimate, then compare with 36156.
Estimate: 524 is about 500 and 69 about 70, 500 × 70 = 35000, so the answer should be near 35000; it is 36156.
11. D. 70
Estimate by multiplying: 82 times roughly what comes close to 5822?
Estimate by multiplying: 82 × 70 is the nearest to 5822, so the answer is about 70 (it is 71).
12. C. 18 × 36 = 6480
Estimate each one: round both numbers to the nearest ten and multiply, and look for an answer that is far off.
Estimate each: the estimate of 18 × 36 is far from 6480 (a digit more or less), so 6480 must be wrong.

Marking: 2 for the working, 1 for the answer, 1 for the sentence.

13. B. Yes, enough
To see if it is enough, round the price up (or down), multiply, and compare with $2,200.
Estimate with $60 each: 36 × 60 = $2,160. Exactly: 36 × 59 = $2,124; compare it with $2,200.
14. 40 mooncakes
Round 1226 to the nearest hundred and 26 to the nearest ten, then divide.
1226 is about 1200 and 26 about 30: 1200 ÷ 30 = 40.
15. B. It is too big
Round 38 and 68 to the nearest ten and multiply to estimate the cost, then compare with 25840.
Estimate: 38 is about 40 and 68 about 70, 40 × 70 = 2800; compare 25840 with it.
16. 1200 dollars
Round 43 and 29 to the nearest ten, then multiply.
43 is about 40 and 29 about 30: 40 × 30 = 1200.
17. 2400 people
Round 293 to the nearest hundred, then multiply by the 8 cars.
293 is about 300: 8 × 300 = 2400.
18. C. Yes, enough
To see if it is enough, round the price up (or down), multiply, and compare with $900.
Estimate with $60 each: 15 × 60 = $900. Exactly: 15 × 51 = $765; compare it with $900.

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