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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 379 · 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 300 + 353? (a) 700 (b) 500 (c) 900
  2. 2.Best estimate of 38 × 86? (a) 3600 (b) 360 (c) 36000
  3. 3.Best estimate of 13 × 43? (a) 40 (b) 400 (c) 4000
  4. 4.Best estimate of 80 × 66? (a) 56000 (b) 5600 (c) 560
  5. 5.Best estimate of 378 + 808? (a) 1000 (b) 1400 (c) 1200
  6. 6.Best estimate of 78 × 82? (a) 640 (b) 64000 (c) 6400
  7. 7.Best estimate of 544 + 549? (a) 1000 (b) 800 (c) 1200
  8. 8.Best estimate of 525 + 314? (a) 800 (b) 600 (c) 1000
  9. 9.Best estimate of 378 + 696? (a) 1300 (b) 1100 (c) 900
  10. 10.Best estimate of 86 × 62? (a) 540 (b) 5400 (c) 54000
  11. 11.Best estimate of 39 × 18? (a) 800 (b) 8000 (c) 80
  12. 12.Best estimate of 61 × 97? (a) 60000 (b) 600 (c) 6000
  13. 13.Best estimate of 60 × 89? (a) 54000 (b) 5400 (c) 540
  14. 14.Best estimate of 98 × 16? (a) 2000 (b) 20000 (c) 200
  15. 15.Best estimate of 18 × 29? (a) 60 (b) 6000 (c) 600
  16. 16.Best estimate of 687 + 310? (a) 1200 (b) 1000 (c) 800
  17. 17.Best estimate of 597 + 662? (a) 1500 (b) 1100 (c) 1300
  18. 18.Best estimate of 44 × 32? (a) 120 (b) 1200 (c) 12000
  19. 19.Best estimate of 16 × 46? (a) 1000 (b) 100 (c) 10000
  20. 20.Best estimate of 97 × 42? (a) 400 (b) 4000 (c) 40000
  21. 21.Best estimate of 24 × 38? (a) 8000 (b) 80 (c) 800
  22. 22.Best estimate of 489 + 178? (a) 900 (b) 500 (c) 700
  23. 23.Best estimate of 60 × 59? (a) 360 (b) 36000 (c) 3600
  24. 24.Best estimate of 803 + 318? (a) 1100 (b) 900 (c) 1300
  25. 25.Best estimate of 162 + 224? (a) 600 (b) 200 (c) 400
  26. 26.Best estimate of 19 × 36? (a) 800 (b) 80 (c) 8000
  27. 27.Best estimate of 26 × 48? (a) 1500 (b) 15000 (c) 150
  28. 28.Best estimate of 71 × 16? (a) 1400 (b) 140 (c) 14000
  29. 29.Best estimate of 698 + 520? (a) 1200 (b) 1000 (c) 1400
  30. 30.Best estimate of 380 + 485? (a) 900 (b) 1100 (c) 700
  31. 31.Best estimate of 505 + 628? (a) 1300 (b) 1100 (c) 900
  32. 32.Best estimate of 396 + 292? (a) 900 (b) 500 (c) 700
  33. 33.Best estimate of 819 + 223? (a) 1200 (b) 800 (c) 1000
  34. 34.Best estimate of 64 × 71? (a) 4200 (b) 42000 (c) 420
  35. 35.Best estimate of 53 × 66? (a) 3500 (b) 35000 (c) 350
  36. 36.Best estimate of 19 × 53? (a) 1000 (b) 100 (c) 10000
  37. 37.Best estimate of 317 + 159? (a) 700 (b) 300 (c) 500
  38. 38.Best estimate of 34 × 20? (a) 600 (b) 60 (c) 6000
  39. 39.Best estimate of 82 × 17? (a) 1600 (b) 160 (c) 16000
  40. 40.Best estimate of 26 × 76? (a) 2400 (b) 24000 (c) 240

Answer key

  1. 700
  2. 3600
  3. 400
  4. 5600
  5. 1200
  6. 6400
  7. 1000
  8. 800
  9. 1100
  10. 5400
  11. 800
  12. 6000
  13. 5400
  14. 2000
  15. 600
  16. 1000
  17. 1300
  18. 1200
  19. 1000
  20. 4000
  21. 800
  22. 700
  23. 3600
  24. 1100
  25. 400
  26. 800
  27. 1500
  28. 1400
  29. 1200
  30. 900
  31. 1100
  32. 700
  33. 1000
  34. 4200
  35. 3500
  36. 1000
  37. 500
  38. 600
  39. 1600
  40. 2400

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