Estimation Strategies — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Estimate 63 times 28 by rounding to 60 and 30 to get 1800.
60 times 30 equals 1,800, giving a quick estimate near the actual product.
2. Estimate 4,832 divided by 24 using compatible numbers 4800 and 24 to get 200.
4,800 divided by 24 equals 200, a clean compatible-number quotient estimate.
3. Estimate 71 times 19 by rounding to 70 and 20 to get 1400.
70 times 20 equals 1,400, a fast estimate near the actual product.
4. A rectangle is 52 cm by 18 cm. Estimate the area using 50 and 20 to get 1000 square cm.
50 times 20 equals 1,000 square cm, a tidy area estimate using rounding.
5. Estimate 5,612 divided by 28 using compatible numbers 5600 and 28 to get 200.
5,600 divided by 28 equals 200, a clean compatible-number quotient estimate.
6. Estimate the perimeter of a 28 cm by 12 cm rectangle using 30 and 10 to get 80 cm.
Two times thirty plus two times ten equals 80, an easy perimeter estimate.
7. Estimate 39 times 51 by rounding both factors to get 2000.
40 times 50 equals 2,000, a fast and close product estimate.
8. Estimate 3,612 divided by 58 using compatible numbers 3600 and 60 to get 60.
3,600 divided by 60 equals 60, a clean compatible-number quotient estimate.
9. Estimate the area of a 41 cm by 19 cm rectangle using 40 and 20 to get 800 square cm.
40 times 20 equals 800 square cm, a quick and close area estimate.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
32 times 19
→ About 600
About 600
8,120 divided by 41
→ About 200
About 200
21 cm by 39 cm perimeter
→ About 120 cm
About 120 cm
612 divided by 31
→ About 20
About 20
Compatible numbers turn tough products and quotients into fast mental math problems.