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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 421 · 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 40 × 56? (a) 24000 (b) 2400 (c) 240
  2. 2.Best estimate of 647 + 728? (a) 1500 (b) 1300 (c) 1100
  3. 3.Best estimate of 38 × 22? (a) 80 (b) 8000 (c) 800
  4. 4.Best estimate of 98 × 63? (a) 600 (b) 6000 (c) 60000
  5. 5.Best estimate of 486 + 174? (a) 900 (b) 500 (c) 700
  6. 6.Best estimate of 729 + 846? (a) 1700 (b) 1300 (c) 1500
  7. 7.Best estimate of 68 × 93? (a) 6300 (b) 630 (c) 63000
  8. 8.Best estimate of 294 + 706? (a) 1200 (b) 800 (c) 1000
  9. 9.Best estimate of 160 + 159? (a) 200 (b) 600 (c) 400
  10. 10.Best estimate of 464 + 580? (a) 1300 (b) 900 (c) 1100
  11. 11.Best estimate of 648 + 331? (a) 1100 (b) 700 (c) 900
  12. 12.Best estimate of 273 + 800? (a) 900 (b) 1300 (c) 1100
  13. 13.Best estimate of 717 + 172? (a) 1100 (b) 900 (c) 700
  14. 14.Best estimate of 599 + 394? (a) 1200 (b) 800 (c) 1000
  15. 15.Best estimate of 477 + 803? (a) 1500 (b) 1100 (c) 1300
  16. 16.Best estimate of 160 + 408? (a) 400 (b) 800 (c) 600
  17. 17.Best estimate of 53 × 36? (a) 200 (b) 20000 (c) 2000
  18. 18.Best estimate of 21 × 29? (a) 6000 (b) 60 (c) 600
  19. 19.Best estimate of 312 + 699? (a) 800 (b) 1200 (c) 1000
  20. 20.Best estimate of 878 + 618? (a) 1500 (b) 1700 (c) 1300
  21. 21.Best estimate of 83 × 16? (a) 1600 (b) 16000 (c) 160
  22. 22.Best estimate of 12 × 83? (a) 8000 (b) 800 (c) 80
  23. 23.Best estimate of 172 + 629? (a) 800 (b) 1000 (c) 600
  24. 24.Best estimate of 667 + 196? (a) 1100 (b) 900 (c) 700
  25. 25.Best estimate of 171 + 648? (a) 600 (b) 800 (c) 1000
  26. 26.Best estimate of 30 × 36? (a) 1200 (b) 12000 (c) 120
  27. 27.Best estimate of 193 + 414? (a) 600 (b) 400 (c) 800
  28. 28.Best estimate of 33 × 71? (a) 2100 (b) 210 (c) 21000
  29. 29.Best estimate of 59 × 26? (a) 1800 (b) 18000 (c) 180
  30. 30.Best estimate of 422 + 345? (a) 700 (b) 900 (c) 500
  31. 31.Best estimate of 57 × 64? (a) 36000 (b) 360 (c) 3600
  32. 32.Best estimate of 709 + 668? (a) 1400 (b) 1600 (c) 1200
  33. 33.Best estimate of 87 × 41? (a) 3600 (b) 36000 (c) 360
  34. 34.Best estimate of 37 × 66? (a) 2800 (b) 280 (c) 28000
  35. 35.Best estimate of 321 + 688? (a) 1200 (b) 800 (c) 1000
  36. 36.Best estimate of 94 × 83? (a) 72000 (b) 7200 (c) 720
  37. 37.Best estimate of 80 × 36? (a) 32000 (b) 3200 (c) 320
  38. 38.Best estimate of 52 × 57? (a) 3000 (b) 30000 (c) 300
  39. 39.Best estimate of 32 × 30? (a) 90 (b) 9000 (c) 900
  40. 40.Best estimate of 66 × 76? (a) 560 (b) 5600 (c) 56000

Answer key

  1. 2400
  2. 1300
  3. 800
  4. 6000
  5. 700
  6. 1500
  7. 6300
  8. 1000
  9. 400
  10. 1100
  11. 900
  12. 1100
  13. 900
  14. 1000
  15. 1300
  16. 600
  17. 2000
  18. 600
  19. 1000
  20. 1500
  21. 1600
  22. 800
  23. 800
  24. 900
  25. 800
  26. 1200
  27. 600
  28. 2100
  29. 1800
  30. 700
  31. 3600
  32. 1400
  33. 3600
  34. 2800
  35. 1000
  36. 7200
  37. 3200
  38. 3000
  39. 900
  40. 5600

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