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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 833 · 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 18 × 16? (a) 40 (b) 400 (c) 4000
  2. 2.Best estimate of 239 + 160? (a) 400 (b) 600 (c) 200
  3. 3.Best estimate of 61 × 24? (a) 12000 (b) 120 (c) 1200
  4. 4.Best estimate of 131 + 784? (a) 1100 (b) 900 (c) 700
  5. 5.Best estimate of 521 + 348? (a) 600 (b) 1000 (c) 800
  6. 6.Best estimate of 477 + 831? (a) 1300 (b) 1100 (c) 1500
  7. 7.Best estimate of 33 × 42? (a) 120 (b) 12000 (c) 1200
  8. 8.Best estimate of 86 × 49? (a) 45000 (b) 4500 (c) 450
  9. 9.Best estimate of 36 × 20? (a) 800 (b) 8000 (c) 80
  10. 10.Best estimate of 533 + 780? (a) 1500 (b) 1300 (c) 1100
  11. 11.Best estimate of 859 + 417? (a) 1300 (b) 1100 (c) 1500
  12. 12.Best estimate of 466 + 291? (a) 600 (b) 1000 (c) 800
  13. 13.Best estimate of 155 + 182? (a) 600 (b) 200 (c) 400
  14. 14.Best estimate of 695 + 610? (a) 1300 (b) 1500 (c) 1100
  15. 15.Best estimate of 96 × 34? (a) 300 (b) 3000 (c) 30000
  16. 16.Best estimate of 96 × 84? (a) 8000 (b) 80000 (c) 800
  17. 17.Best estimate of 92 × 87? (a) 8100 (b) 810 (c) 81000
  18. 18.Best estimate of 97 × 82? (a) 8000 (b) 800 (c) 80000
  19. 19.Best estimate of 56 × 23? (a) 12000 (b) 1200 (c) 120
  20. 20.Best estimate of 199 + 212? (a) 200 (b) 600 (c) 400
  21. 21.Best estimate of 74 × 46? (a) 3500 (b) 35000 (c) 350
  22. 22.Best estimate of 19 × 91? (a) 1800 (b) 18000 (c) 180
  23. 23.Best estimate of 91 × 83? (a) 72000 (b) 7200 (c) 720
  24. 24.Best estimate of 631 + 751? (a) 1400 (b) 1600 (c) 1200
  25. 25.Best estimate of 61 × 46? (a) 300 (b) 30000 (c) 3000
  26. 26.Best estimate of 20 × 81? (a) 160 (b) 1600 (c) 16000
  27. 27.Best estimate of 78 × 82? (a) 64000 (b) 640 (c) 6400
  28. 28.Best estimate of 41 × 42? (a) 1600 (b) 160 (c) 16000
  29. 29.Best estimate of 36 × 81? (a) 32000 (b) 3200 (c) 320
  30. 30.Best estimate of 89 × 81? (a) 7200 (b) 72000 (c) 720
  31. 31.Best estimate of 354 + 801? (a) 1400 (b) 1200 (c) 1000
  32. 32.Best estimate of 782 + 708? (a) 1500 (b) 1700 (c) 1300
  33. 33.Best estimate of 311 + 666? (a) 800 (b) 1000 (c) 1200
  34. 34.Best estimate of 165 + 151? (a) 400 (b) 200 (c) 600
  35. 35.Best estimate of 446 + 265? (a) 700 (b) 500 (c) 900
  36. 36.Best estimate of 185 + 867? (a) 1100 (b) 900 (c) 1300
  37. 37.Best estimate of 30 × 30? (a) 9000 (b) 90 (c) 900
  38. 38.Best estimate of 18 × 22? (a) 40 (b) 400 (c) 4000
  39. 39.Best estimate of 34 × 61? (a) 180 (b) 1800 (c) 18000
  40. 40.Best estimate of 77 × 17? (a) 160 (b) 1600 (c) 16000

Answer key

  1. 400
  2. 400
  3. 1200
  4. 900
  5. 800
  6. 1300
  7. 1200
  8. 4500
  9. 800
  10. 1300
  11. 1300
  12. 800
  13. 400
  14. 1300
  15. 3000
  16. 8000
  17. 8100
  18. 8000
  19. 1200
  20. 400
  21. 3500
  22. 1800
  23. 7200
  24. 1400
  25. 3000
  26. 1600
  27. 6400
  28. 1600
  29. 3200
  30. 7200
  31. 1200
  32. 1500
  33. 1000
  34. 400
  35. 700
  36. 1100
  37. 900
  38. 400
  39. 1800
  40. 1600

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