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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 850 · 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 82 × 21? (a) 160 (b) 1600 (c) 16000
  2. 2.Best estimate of 80 × 34? (a) 24000 (b) 240 (c) 2400
  3. 3.Best estimate of 24 × 76? (a) 16000 (b) 1600 (c) 160
  4. 4.Best estimate of 657 + 460? (a) 1000 (b) 1400 (c) 1200
  5. 5.Best estimate of 481 + 437? (a) 1100 (b) 700 (c) 900
  6. 6.Best estimate of 44 × 47? (a) 200 (b) 2000 (c) 20000
  7. 7.Best estimate of 57 × 36? (a) 2400 (b) 240 (c) 24000
  8. 8.Best estimate of 134 + 500? (a) 600 (b) 800 (c) 400
  9. 9.Best estimate of 70 × 58? (a) 42000 (b) 4200 (c) 420
  10. 10.Best estimate of 532 + 657? (a) 1200 (b) 1400 (c) 1000
  11. 11.Best estimate of 17 × 89? (a) 18000 (b) 180 (c) 1800
  12. 12.Best estimate of 84 × 26? (a) 240 (b) 24000 (c) 2400
  13. 13.Best estimate of 68 × 66? (a) 490 (b) 4900 (c) 49000
  14. 14.Best estimate of 847 + 402? (a) 1400 (b) 1000 (c) 1200
  15. 15.Best estimate of 76 × 70? (a) 56000 (b) 560 (c) 5600
  16. 16.Best estimate of 867 + 131? (a) 1200 (b) 1000 (c) 800
  17. 17.Best estimate of 122 + 618? (a) 500 (b) 900 (c) 700
  18. 18.Best estimate of 79 × 19? (a) 160 (b) 16000 (c) 1600
  19. 19.Best estimate of 626 + 404? (a) 1200 (b) 1000 (c) 800
  20. 20.Best estimate of 33 × 58? (a) 180 (b) 1800 (c) 18000
  21. 21.Best estimate of 92 × 19? (a) 18000 (b) 1800 (c) 180
  22. 22.Best estimate of 727 + 676? (a) 1200 (b) 1600 (c) 1400
  23. 23.Best estimate of 651 + 393? (a) 1300 (b) 1100 (c) 900
  24. 24.Best estimate of 622 + 701? (a) 1500 (b) 1100 (c) 1300
  25. 25.Best estimate of 52 × 79? (a) 40000 (b) 400 (c) 4000
  26. 26.Best estimate of 74 × 97? (a) 7000 (b) 700 (c) 70000
  27. 27.Best estimate of 552 + 189? (a) 1000 (b) 800 (c) 600
  28. 28.Best estimate of 89 × 92? (a) 810 (b) 8100 (c) 81000
  29. 29.Best estimate of 823 + 733? (a) 1500 (b) 1700 (c) 1300
  30. 30.Best estimate of 536 + 220? (a) 900 (b) 500 (c) 700
  31. 31.Best estimate of 262 + 812? (a) 1100 (b) 900 (c) 1300
  32. 32.Best estimate of 27 × 56? (a) 1800 (b) 18000 (c) 180
  33. 33.Best estimate of 90 × 13? (a) 900 (b) 90 (c) 9000
  34. 34.Best estimate of 310 + 590? (a) 700 (b) 900 (c) 1100
  35. 35.Best estimate of 68 × 54? (a) 350 (b) 35000 (c) 3500
  36. 36.Best estimate of 96 × 21? (a) 20000 (b) 2000 (c) 200
  37. 37.Best estimate of 56 × 59? (a) 36000 (b) 360 (c) 3600
  38. 38.Best estimate of 40 × 28? (a) 1200 (b) 12000 (c) 120
  39. 39.Best estimate of 86 × 41? (a) 36000 (b) 3600 (c) 360
  40. 40.Best estimate of 17 × 92? (a) 1800 (b) 18000 (c) 180

Answer key

  1. 1600
  2. 2400
  3. 1600
  4. 1200
  5. 900
  6. 2000
  7. 2400
  8. 600
  9. 4200
  10. 1200
  11. 1800
  12. 2400
  13. 4900
  14. 1200
  15. 5600
  16. 1000
  17. 700
  18. 1600
  19. 1000
  20. 1800
  21. 1800
  22. 1400
  23. 1100
  24. 1300
  25. 4000
  26. 7000
  27. 800
  28. 8100
  29. 1500
  30. 700
  31. 1100
  32. 1800
  33. 900
  34. 900
  35. 3500
  36. 2000
  37. 3600
  38. 1200
  39. 3600
  40. 1800

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