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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 666 · 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 70 × 52? (a) 35000 (b) 3500 (c) 350
  2. 2.Best estimate of 410 + 203? (a) 400 (b) 600 (c) 800
  3. 3.Best estimate of 557 + 389? (a) 1000 (b) 1200 (c) 800
  4. 4.Best estimate of 434 + 735? (a) 900 (b) 1300 (c) 1100
  5. 5.Best estimate of 66 × 28? (a) 21000 (b) 2100 (c) 210
  6. 6.Best estimate of 582 + 701? (a) 1500 (b) 1300 (c) 1100
  7. 7.Best estimate of 319 + 234? (a) 500 (b) 300 (c) 700
  8. 8.Best estimate of 473 + 140? (a) 800 (b) 600 (c) 400
  9. 9.Best estimate of 705 + 304? (a) 800 (b) 1200 (c) 1000
  10. 10.Best estimate of 40 × 82? (a) 320 (b) 3200 (c) 32000
  11. 11.Best estimate of 547 + 133? (a) 400 (b) 600 (c) 800
  12. 12.Best estimate of 17 × 88? (a) 1800 (b) 18000 (c) 180
  13. 13.Best estimate of 618 + 795? (a) 1600 (b) 1400 (c) 1200
  14. 14.Best estimate of 79 × 78? (a) 64000 (b) 6400 (c) 640
  15. 15.Best estimate of 13 × 80? (a) 800 (b) 80 (c) 8000
  16. 16.Best estimate of 96 × 26? (a) 3000 (b) 300 (c) 30000
  17. 17.Best estimate of 640 + 226? (a) 1000 (b) 600 (c) 800
  18. 18.Best estimate of 12 × 48? (a) 50 (b) 5000 (c) 500
  19. 19.Best estimate of 37 × 71? (a) 2800 (b) 280 (c) 28000
  20. 20.Best estimate of 60 × 30? (a) 18000 (b) 180 (c) 1800
  21. 21.Best estimate of 36 × 86? (a) 36000 (b) 360 (c) 3600
  22. 22.Best estimate of 97 × 82? (a) 8000 (b) 800 (c) 80000
  23. 23.Best estimate of 13 × 66? (a) 700 (b) 7000 (c) 70
  24. 24.Best estimate of 539 + 283? (a) 600 (b) 1000 (c) 800
  25. 25.Best estimate of 861 + 829? (a) 1500 (b) 1900 (c) 1700
  26. 26.Best estimate of 24 × 17? (a) 400 (b) 40 (c) 4000
  27. 27.Best estimate of 82 × 29? (a) 240 (b) 24000 (c) 2400
  28. 28.Best estimate of 863 + 348? (a) 1400 (b) 1000 (c) 1200
  29. 29.Best estimate of 77 × 21? (a) 1600 (b) 16000 (c) 160
  30. 30.Best estimate of 379 + 637? (a) 800 (b) 1200 (c) 1000
  31. 31.Best estimate of 17 × 83? (a) 1600 (b) 160 (c) 16000
  32. 32.Best estimate of 96 × 74? (a) 7000 (b) 70000 (c) 700
  33. 33.Best estimate of 97 × 54? (a) 50000 (b) 5000 (c) 500
  34. 34.Best estimate of 168 + 839? (a) 800 (b) 1000 (c) 1200
  35. 35.Best estimate of 409 + 512? (a) 700 (b) 1100 (c) 900
  36. 36.Best estimate of 46 × 44? (a) 20000 (b) 2000 (c) 200
  37. 37.Best estimate of 20 × 83? (a) 16000 (b) 160 (c) 1600
  38. 38.Best estimate of 394 + 206? (a) 800 (b) 400 (c) 600
  39. 39.Best estimate of 37 × 23? (a) 8000 (b) 80 (c) 800
  40. 40.Best estimate of 612 + 146? (a) 500 (b) 700 (c) 900

Answer key

  1. 3500
  2. 600
  3. 1000
  4. 1100
  5. 2100
  6. 1300
  7. 500
  8. 600
  9. 1000
  10. 3200
  11. 600
  12. 1800
  13. 1400
  14. 6400
  15. 800
  16. 3000
  17. 800
  18. 500
  19. 2800
  20. 1800
  21. 3600
  22. 8000
  23. 700
  24. 800
  25. 1700
  26. 400
  27. 2400
  28. 1200
  29. 1600
  30. 1000
  31. 1600
  32. 7000
  33. 5000
  34. 1000
  35. 900
  36. 2000
  37. 1600
  38. 600
  39. 800
  40. 700

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