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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 166 · 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 439 + 417? (a) 800 (b) 1000 (c) 600
  2. 2.Best estimate of 772 + 696? (a) 1300 (b) 1500 (c) 1700
  3. 3.Best estimate of 170 + 153? (a) 200 (b) 600 (c) 400
  4. 4.Best estimate of 361 + 581? (a) 800 (b) 1200 (c) 1000
  5. 5.Best estimate of 210 + 493? (a) 900 (b) 700 (c) 500
  6. 6.Best estimate of 70 × 47? (a) 350 (b) 35000 (c) 3500
  7. 7.Best estimate of 63 × 17? (a) 120 (b) 12000 (c) 1200
  8. 8.Best estimate of 46 × 90? (a) 450 (b) 4500 (c) 45000
  9. 9.Best estimate of 438 + 754? (a) 1200 (b) 1400 (c) 1000
  10. 10.Best estimate of 36 × 26? (a) 12000 (b) 1200 (c) 120
  11. 11.Best estimate of 474 + 182? (a) 500 (b) 700 (c) 900
  12. 12.Best estimate of 211 + 628? (a) 800 (b) 600 (c) 1000
  13. 13.Best estimate of 73 × 90? (a) 6300 (b) 63000 (c) 630
  14. 14.Best estimate of 128 + 323? (a) 200 (b) 600 (c) 400
  15. 15.Best estimate of 200 + 668? (a) 700 (b) 900 (c) 1100
  16. 16.Best estimate of 132 + 871? (a) 1200 (b) 800 (c) 1000
  17. 17.Best estimate of 74 × 57? (a) 42000 (b) 4200 (c) 420
  18. 18.Best estimate of 581 + 822? (a) 1200 (b) 1400 (c) 1600
  19. 19.Best estimate of 493 + 601? (a) 900 (b) 1300 (c) 1100
  20. 20.Best estimate of 21 × 89? (a) 1800 (b) 180 (c) 18000
  21. 21.Best estimate of 76 × 69? (a) 5600 (b) 560 (c) 56000
  22. 22.Best estimate of 30 × 69? (a) 2100 (b) 21000 (c) 210
  23. 23.Best estimate of 304 + 846? (a) 1100 (b) 1300 (c) 900
  24. 24.Best estimate of 88 × 44? (a) 3600 (b) 360 (c) 36000
  25. 25.Best estimate of 553 + 870? (a) 1500 (b) 1700 (c) 1300
  26. 26.Best estimate of 96 × 29? (a) 3000 (b) 300 (c) 30000
  27. 27.Best estimate of 96 × 70? (a) 70000 (b) 700 (c) 7000
  28. 28.Best estimate of 72 × 91? (a) 6300 (b) 630 (c) 63000
  29. 29.Best estimate of 28 × 46? (a) 150 (b) 15000 (c) 1500
  30. 30.Best estimate of 809 + 256? (a) 900 (b) 1100 (c) 1300
  31. 31.Best estimate of 128 + 266? (a) 200 (b) 400 (c) 600
  32. 32.Best estimate of 48 × 76? (a) 40000 (b) 400 (c) 4000
  33. 33.Best estimate of 821 + 747? (a) 1300 (b) 1500 (c) 1700
  34. 34.Best estimate of 27 × 69? (a) 2100 (b) 21000 (c) 210
  35. 35.Best estimate of 90 × 57? (a) 540 (b) 54000 (c) 5400
  36. 36.Best estimate of 20 × 20? (a) 40 (b) 400 (c) 4000
  37. 37.Best estimate of 876 + 139? (a) 1000 (b) 800 (c) 1200
  38. 38.Best estimate of 52 × 34? (a) 150 (b) 1500 (c) 15000
  39. 39.Best estimate of 84 × 91? (a) 720 (b) 72000 (c) 7200
  40. 40.Best estimate of 310 + 490? (a) 800 (b) 1000 (c) 600

Answer key

  1. 800
  2. 1500
  3. 400
  4. 1000
  5. 700
  6. 3500
  7. 1200
  8. 4500
  9. 1200
  10. 1200
  11. 700
  12. 800
  13. 6300
  14. 400
  15. 900
  16. 1000
  17. 4200
  18. 1400
  19. 1100
  20. 1800
  21. 5600
  22. 2100
  23. 1100
  24. 3600
  25. 1500
  26. 3000
  27. 7000
  28. 6300
  29. 1500
  30. 1100
  31. 400
  32. 4000
  33. 1500
  34. 2100
  35. 5400
  36. 400
  37. 1000
  38. 1500
  39. 7200
  40. 800

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