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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 457 · 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 14 × 28? (a) 30 (b) 300 (c) 3000
  2. 2.Best estimate of 634 + 239? (a) 800 (b) 600 (c) 1000
  3. 3.Best estimate of 58 × 19? (a) 120 (b) 12000 (c) 1200
  4. 4.Best estimate of 37 × 72? (a) 28000 (b) 2800 (c) 280
  5. 5.Best estimate of 40 × 41? (a) 1600 (b) 16000 (c) 160
  6. 6.Best estimate of 20 × 22? (a) 4000 (b) 40 (c) 400
  7. 7.Best estimate of 831 + 870? (a) 1500 (b) 1900 (c) 1700
  8. 8.Best estimate of 619 + 220? (a) 800 (b) 600 (c) 1000
  9. 9.Best estimate of 98 × 36? (a) 400 (b) 40000 (c) 4000
  10. 10.Best estimate of 529 + 154? (a) 700 (b) 500 (c) 900
  11. 11.Best estimate of 330 + 412? (a) 500 (b) 700 (c) 900
  12. 12.Best estimate of 271 + 829? (a) 900 (b) 1100 (c) 1300
  13. 13.Best estimate of 430 + 727? (a) 1100 (b) 1300 (c) 900
  14. 14.Best estimate of 601 + 598? (a) 1200 (b) 1400 (c) 1000
  15. 15.Best estimate of 388 + 375? (a) 1000 (b) 800 (c) 600
  16. 16.Best estimate of 94 × 90? (a) 810 (b) 8100 (c) 81000
  17. 17.Best estimate of 96 × 94? (a) 900 (b) 90000 (c) 9000
  18. 18.Best estimate of 799 + 194? (a) 800 (b) 1200 (c) 1000
  19. 19.Best estimate of 81 × 74? (a) 56000 (b) 5600 (c) 560
  20. 20.Best estimate of 635 + 635? (a) 1400 (b) 1200 (c) 1000
  21. 21.Best estimate of 23 × 62? (a) 120 (b) 1200 (c) 12000
  22. 22.Best estimate of 21 × 34? (a) 6000 (b) 60 (c) 600
  23. 23.Best estimate of 700 + 694? (a) 1200 (b) 1600 (c) 1400
  24. 24.Best estimate of 38 × 74? (a) 280 (b) 2800 (c) 28000
  25. 25.Best estimate of 84 × 77? (a) 640 (b) 6400 (c) 64000
  26. 26.Best estimate of 20 × 20? (a) 4000 (b) 400 (c) 40
  27. 27.Best estimate of 61 × 34? (a) 18000 (b) 1800 (c) 180
  28. 28.Best estimate of 34 × 77? (a) 24000 (b) 2400 (c) 240
  29. 29.Best estimate of 420 + 466? (a) 900 (b) 1100 (c) 700
  30. 30.Best estimate of 89 × 80? (a) 7200 (b) 720 (c) 72000
  31. 31.Best estimate of 81 × 69? (a) 5600 (b) 560 (c) 56000
  32. 32.Best estimate of 56 × 66? (a) 4200 (b) 42000 (c) 420
  33. 33.Best estimate of 83 × 18? (a) 16000 (b) 160 (c) 1600
  34. 34.Best estimate of 68 × 12? (a) 70 (b) 7000 (c) 700
  35. 35.Best estimate of 641 + 226? (a) 600 (b) 1000 (c) 800
  36. 36.Best estimate of 57 × 96? (a) 600 (b) 60000 (c) 6000
  37. 37.Best estimate of 305 + 405? (a) 700 (b) 900 (c) 500
  38. 38.Best estimate of 34 × 84? (a) 240 (b) 2400 (c) 24000
  39. 39.Best estimate of 16 × 32? (a) 6000 (b) 60 (c) 600
  40. 40.Best estimate of 131 + 737? (a) 800 (b) 1000 (c) 600

Answer key

  1. 300
  2. 800
  3. 1200
  4. 2800
  5. 1600
  6. 400
  7. 1700
  8. 800
  9. 4000
  10. 700
  11. 700
  12. 1100
  13. 1100
  14. 1200
  15. 800
  16. 8100
  17. 9000
  18. 1000
  19. 5600
  20. 1200
  21. 1200
  22. 600
  23. 1400
  24. 2800
  25. 6400
  26. 400
  27. 1800
  28. 2400
  29. 900
  30. 7200
  31. 5600
  32. 4200
  33. 1600
  34. 700
  35. 800
  36. 6000
  37. 700
  38. 2400
  39. 600
  40. 800

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