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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 225 · 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 21 × 33? (a) 60 (b) 6000 (c) 600
  2. 2.Best estimate of 61 × 21? (a) 1200 (b) 12000 (c) 120
  3. 3.Best estimate of 23 × 89? (a) 1800 (b) 180 (c) 18000
  4. 4.Best estimate of 521 + 829? (a) 1300 (b) 1100 (c) 1500
  5. 5.Best estimate of 96 × 66? (a) 70000 (b) 7000 (c) 700
  6. 6.Best estimate of 759 + 314? (a) 900 (b) 1300 (c) 1100
  7. 7.Best estimate of 238 + 804? (a) 1000 (b) 1200 (c) 800
  8. 8.Best estimate of 701 + 853? (a) 1800 (b) 1600 (c) 1400
  9. 9.Best estimate of 28 × 22? (a) 600 (b) 60 (c) 6000
  10. 10.Best estimate of 46 × 74? (a) 35000 (b) 350 (c) 3500
  11. 11.Best estimate of 73 × 30? (a) 21000 (b) 2100 (c) 210
  12. 12.Best estimate of 78 × 37? (a) 3200 (b) 32000 (c) 320
  13. 13.Best estimate of 96 × 49? (a) 500 (b) 50000 (c) 5000
  14. 14.Best estimate of 58 × 21? (a) 1200 (b) 120 (c) 12000
  15. 15.Best estimate of 97 × 66? (a) 70000 (b) 7000 (c) 700
  16. 16.Best estimate of 42 × 84? (a) 3200 (b) 320 (c) 32000
  17. 17.Best estimate of 348 + 336? (a) 400 (b) 600 (c) 800
  18. 18.Best estimate of 39 × 81? (a) 32000 (b) 320 (c) 3200
  19. 19.Best estimate of 46 × 27? (a) 15000 (b) 1500 (c) 150
  20. 20.Best estimate of 135 + 831? (a) 900 (b) 1100 (c) 700
  21. 21.Best estimate of 740 + 135? (a) 1000 (b) 800 (c) 600
  22. 22.Best estimate of 600 + 134? (a) 500 (b) 700 (c) 900
  23. 23.Best estimate of 30 × 74? (a) 210 (b) 2100 (c) 21000
  24. 24.Best estimate of 293 + 619? (a) 900 (b) 700 (c) 1100
  25. 25.Best estimate of 242 + 137? (a) 100 (b) 300 (c) 500
  26. 26.Best estimate of 66 × 30? (a) 2100 (b) 210 (c) 21000
  27. 27.Best estimate of 14 × 96? (a) 1000 (b) 10000 (c) 100
  28. 28.Best estimate of 16 × 32? (a) 600 (b) 60 (c) 6000
  29. 29.Best estimate of 199 + 180? (a) 400 (b) 200 (c) 600
  30. 30.Best estimate of 22 × 23? (a) 40 (b) 400 (c) 4000
  31. 31.Best estimate of 23 × 36? (a) 800 (b) 8000 (c) 80
  32. 32.Best estimate of 26 × 56? (a) 180 (b) 18000 (c) 1800
  33. 33.Best estimate of 333 + 757? (a) 1100 (b) 1300 (c) 900
  34. 34.Best estimate of 94 × 22? (a) 180 (b) 1800 (c) 18000
  35. 35.Best estimate of 97 × 87? (a) 900 (b) 90000 (c) 9000
  36. 36.Best estimate of 724 + 320? (a) 1200 (b) 1000 (c) 800
  37. 37.Best estimate of 84 × 13? (a) 80 (b) 800 (c) 8000
  38. 38.Best estimate of 43 × 69? (a) 2800 (b) 28000 (c) 280
  39. 39.Best estimate of 13 × 78? (a) 80 (b) 8000 (c) 800
  40. 40.Best estimate of 17 × 93? (a) 1800 (b) 18000 (c) 180

Answer key

  1. 600
  2. 1200
  3. 1800
  4. 1300
  5. 7000
  6. 1100
  7. 1000
  8. 1600
  9. 600
  10. 3500
  11. 2100
  12. 3200
  13. 5000
  14. 1200
  15. 7000
  16. 3200
  17. 600
  18. 3200
  19. 1500
  20. 900
  21. 800
  22. 700
  23. 2100
  24. 900
  25. 300
  26. 2100
  27. 1000
  28. 600
  29. 400
  30. 400
  31. 800
  32. 1800
  33. 1100
  34. 1800
  35. 9000
  36. 1000
  37. 800
  38. 2800
  39. 800
  40. 1800

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