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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 475 · 40 questions
TalentJR

How to do it in your head (Round, then work): Round each number: 2-digit numbers to the nearest ten, 3-digit numbers to the nearest hundred. Do the easy sum with the round numbers. Choose the option closest to your estimate.

NameDateTime takenScore ___ / 40
  1. 1.Best estimate of 86 × 20? (a) 18000 (b) 180 (c) 1800
  2. 2.Best estimate of 646 + 284? (a) 900 (b) 1100 (c) 700
  3. 3.Best estimate of 76 × 82? (a) 640 (b) 64000 (c) 6400
  4. 4.Best estimate of 17 × 68? (a) 14000 (b) 1400 (c) 140
  5. 5.Best estimate of 24 × 50? (a) 1000 (b) 10000 (c) 100
  6. 6.Best estimate of 79 × 39? (a) 32000 (b) 320 (c) 3200
  7. 7.Best estimate of 67 × 21? (a) 14000 (b) 1400 (c) 140
  8. 8.Best estimate of 23 × 48? (a) 100 (b) 10000 (c) 1000
  9. 9.Best estimate of 12 × 46? (a) 500 (b) 50 (c) 5000
  10. 10.Best estimate of 18 × 91? (a) 1800 (b) 18000 (c) 180
  11. 11.Best estimate of 307 + 799? (a) 1300 (b) 1100 (c) 900
  12. 12.Best estimate of 314 + 662? (a) 800 (b) 1200 (c) 1000
  13. 13.Best estimate of 163 + 724? (a) 700 (b) 900 (c) 1100
  14. 14.Best estimate of 773 + 237? (a) 1000 (b) 1200 (c) 800
  15. 15.Best estimate of 86 × 76? (a) 72000 (b) 7200 (c) 720
  16. 16.Best estimate of 28 × 47? (a) 1500 (b) 15000 (c) 150
  17. 17.Best estimate of 31 × 53? (a) 15000 (b) 1500 (c) 150
  18. 18.Best estimate of 89 × 74? (a) 6300 (b) 630 (c) 63000
  19. 19.Best estimate of 42 × 43? (a) 16000 (b) 1600 (c) 160
  20. 20.Best estimate of 96 × 48? (a) 500 (b) 5000 (c) 50000
  21. 21.Best estimate of 489 + 491? (a) 800 (b) 1200 (c) 1000
  22. 22.Best estimate of 84 × 82? (a) 64000 (b) 6400 (c) 640
  23. 23.Best estimate of 84 × 66? (a) 5600 (b) 56000 (c) 560
  24. 24.Best estimate of 221 + 494? (a) 500 (b) 700 (c) 900
  25. 25.Best estimate of 22 × 77? (a) 1600 (b) 16000 (c) 160
  26. 26.Best estimate of 183 + 373? (a) 600 (b) 400 (c) 800
  27. 27.Best estimate of 41 × 41? (a) 16000 (b) 160 (c) 1600
  28. 28.Best estimate of 96 × 69? (a) 70000 (b) 700 (c) 7000
  29. 29.Best estimate of 36 × 94? (a) 36000 (b) 360 (c) 3600
  30. 30.Best estimate of 74 × 41? (a) 2800 (b) 28000 (c) 280
  31. 31.Best estimate of 92 × 81? (a) 7200 (b) 72000 (c) 720
  32. 32.Best estimate of 403 + 738? (a) 900 (b) 1100 (c) 1300
  33. 33.Best estimate of 67 × 48? (a) 350 (b) 35000 (c) 3500
  34. 34.Best estimate of 50 × 20? (a) 100 (b) 1000 (c) 10000
  35. 35.Best estimate of 37 × 63? (a) 24000 (b) 240 (c) 2400
  36. 36.Best estimate of 627 + 338? (a) 700 (b) 1100 (c) 900
  37. 37.Best estimate of 86 × 52? (a) 450 (b) 4500 (c) 45000
  38. 38.Best estimate of 44 × 93? (a) 36000 (b) 360 (c) 3600
  39. 39.Best estimate of 63 × 39? (a) 2400 (b) 240 (c) 24000
  40. 40.Best estimate of 51 × 76? (a) 400 (b) 40000 (c) 4000

Answer key

  1. 1800
  2. 900
  3. 6400
  4. 1400
  5. 1000
  6. 3200
  7. 1400
  8. 1000
  9. 500
  10. 1800
  11. 1100
  12. 1000
  13. 900
  14. 1000
  15. 7200
  16. 1500
  17. 1500
  18. 6300
  19. 1600
  20. 5000
  21. 1000
  22. 6400
  23. 5600
  24. 700
  25. 1600
  26. 600
  27. 1600
  28. 7000
  29. 3600
  30. 2800
  31. 7200
  32. 1100
  33. 3500
  34. 1000
  35. 2400
  36. 900
  37. 4500
  38. 3600
  39. 2400
  40. 4000

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