Multiplying, dividing and mixed operations · Ages 8–9

Estimate first, then work it out worksheet

Part of: Multiplying by a one-digit number

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Multiplying, dividing and mixed operations · Ages 8–9

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

7.Which of these is closest to 86 × 6?
- A. 96
- B. 540
- C. 5400
- D. 480
Choose the right answer
Answer:
8.Which of these is closest to 52 × 3?
- A. 180
- B. 53
- C. 150
- D. 1500
Choose the right answer
Answer:
9.Between which two numbers does 63 × 6 lie?
- A. Between 360 and 420
- B. Between 3600 and 4200
- C. Between 300 and 360
- D. Between 420 and 480
Choose the right answer
Answer:
10.14 × 7 = 980. Estimate first: this answer is reasonable.
True or false?
Answer:
11.81 × 3 = 2430. Estimate first: this answer is reasonable.
True or false?
Answer:
12.Between which two numbers does 91 × 6 lie?
- A. Between 540 and 600
- B. Between 480 and 540
- C. Between 5400 and 6000
- D. Between 600 and 660
Choose the right answer
Answer:

13.A cinema has 38 seats in each row and 7 rows. Rounding the seats in a row to the nearest ten, about how many seats does it have?
Working:
Answer:
14.Ka-yee skips 52 times a day. Rounding 52 to the nearest ten, about how many skips is that in a week (7 days)?
Working:
Answer:
15.A box of mooncakes costs $96, and Tsz-ching buys 6 boxes. Rounding the price to the nearest ten, about how many dollars is that?
Working:
Answer:
16.May has $90 and wants 7 water bottles at $12 each. May has enough money.
True or false?
Working:
Answer:
17.A coach travels 186 km a day. Rounding 186 to the nearest hundred, about how many km does it travel in 5 days?
Working:
Answer:
18.A box of mooncakes costs $91, and May buys 5 boxes. Rounding the price to the nearest ten, about how many dollars is that?
Working:
Answer:

Show the answers and working

Estimate first, then work it out worksheet: Answers and working

1. 180
Round 25 to the nearest ten first, then multiply by 6.
The nearest ten to 25 is 30: 30 × 6 = 180.
2. 240
Round 26 to the nearest ten first, then multiply by 8.
The nearest ten to 26 is 30: 30 × 8 = 240.
3. 450
Round 88 to the nearest ten first, then multiply by 5.
The nearest ten to 88 is 90: 90 × 5 = 450.
4. 4000
Round 952 to the nearest hundred first, then multiply by 4.
The nearest hundred to 952 is 1000: 1000 × 4 = 4000.
5. 400
Round 152 to the nearest hundred first, then multiply by 2.
The nearest hundred to 152 is 200: 200 × 2 = 400.
6. 7200
Round 795 to the nearest hundred first, then multiply by 9.
The nearest hundred to 795 is 800: 800 × 9 = 7200.

7. B. 540
Round 86 to the nearest ten, multiply by 6, then see which option is closest.
86 is about 90, and 90 × 6 = 540, so the answer is closest to 540.
8. C. 150
Round 52 to the nearest ten, multiply by 3, then see which option is closest.
52 is about 50, and 50 × 3 = 150, so the answer is closest to 150.
9. A. Between 360 and 420
Which two tens does 63 lie between? Multiply each of them by 6.
63 lies between two tens, so 63 × 6 lies between 360 and 420.
10. False
Estimate first: 14 is about how many tens? About how much is that times 7? Then compare with 980.
Estimate: 14 is about 10, and 10 × 7 = 70. Compare 980 with 70: close is reasonable; a zero too many is not.
11. False
Estimate first: 81 is about how many tens? About how much is that times 3? Then compare with 2430.
Estimate: 81 is about 80, and 80 × 3 = 240. Compare 2430 with 240: close is reasonable; a zero too many is not.
12. A. Between 540 and 600
Which two tens does 91 lie between? Multiply each of them by 6.
91 lies between two tens, so 91 × 6 lies between 540 and 600.

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

13. 280 seats
Round 38 to the nearest ten first, then multiply by 7 rows.
38 is about 40: 40 × 7 = 280.
14. 350 skips
Round 52 to the nearest ten first, then multiply by 7 days.
52 is about 50: 50 × 7 = 350.
15. 600 dollars
Round $96 to the nearest ten first, then multiply by 6 boxes.
$96 is about $100: 100 × 6 = 600, so about $600.
16. True
Estimate first: about how many tens is $12? About how much are 7? If it's close to 90, work out 12 × 7 exactly.
Estimate first: 10 × 7 = 70; then exactly: 12 × 7 = 84. Compare 84 with 90 to see if it is enough.
17. 1000 km
Round 186 to the nearest hundred first, then multiply by 5 days.
186 is about 200: 200 × 5 = 1000.
18. 450 dollars
Round $91 to the nearest ten first, then multiply by 5 boxes.
$91 is about $90: 90 × 5 = 450, so about $450.

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