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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 247 · 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 42 × 39? (a) 160 (b) 16000 (c) 1600
  2. 2.Best estimate of 70 × 71? (a) 490 (b) 49000 (c) 4900
  3. 3.Best estimate of 36 × 86? (a) 360 (b) 36000 (c) 3600
  4. 4.Best estimate of 62 × 16? (a) 120 (b) 12000 (c) 1200
  5. 5.Best estimate of 742 + 222? (a) 900 (b) 1100 (c) 700
  6. 6.Best estimate of 490 + 795? (a) 1500 (b) 1100 (c) 1300
  7. 7.Best estimate of 96 × 79? (a) 80000 (b) 800 (c) 8000
  8. 8.Best estimate of 651 + 440? (a) 1300 (b) 1100 (c) 900
  9. 9.Best estimate of 210 + 320? (a) 700 (b) 500 (c) 300
  10. 10.Best estimate of 30 × 37? (a) 120 (b) 12000 (c) 1200
  11. 11.Best estimate of 349 + 207? (a) 500 (b) 700 (c) 300
  12. 12.Best estimate of 27 × 76? (a) 2400 (b) 240 (c) 24000
  13. 13.Best estimate of 86 × 83? (a) 720 (b) 7200 (c) 72000
  14. 14.Best estimate of 46 × 92? (a) 45000 (b) 4500 (c) 450
  15. 15.Best estimate of 607 + 128? (a) 500 (b) 900 (c) 700
  16. 16.Best estimate of 56 × 16? (a) 120 (b) 1200 (c) 12000
  17. 17.Best estimate of 12 × 82? (a) 800 (b) 8000 (c) 80
  18. 18.Best estimate of 316 + 163? (a) 300 (b) 700 (c) 500
  19. 19.Best estimate of 61 × 68? (a) 42000 (b) 420 (c) 4200
  20. 20.Best estimate of 40 × 50? (a) 200 (b) 2000 (c) 20000
  21. 21.Best estimate of 648 + 358? (a) 1200 (b) 800 (c) 1000
  22. 22.Best estimate of 39 × 68? (a) 28000 (b) 2800 (c) 280
  23. 23.Best estimate of 83 × 86? (a) 72000 (b) 720 (c) 7200
  24. 24.Best estimate of 60 × 91? (a) 54000 (b) 540 (c) 5400
  25. 25.Best estimate of 691 + 395? (a) 900 (b) 1300 (c) 1100
  26. 26.Best estimate of 70 × 38? (a) 280 (b) 2800 (c) 28000
  27. 27.Best estimate of 435 + 538? (a) 700 (b) 900 (c) 1100
  28. 28.Best estimate of 81 × 14? (a) 800 (b) 80 (c) 8000
  29. 29.Best estimate of 64 × 86? (a) 5400 (b) 540 (c) 54000
  30. 30.Best estimate of 772 + 177? (a) 800 (b) 1200 (c) 1000
  31. 31.Best estimate of 410 + 308? (a) 700 (b) 900 (c) 500
  32. 32.Best estimate of 161 + 245? (a) 200 (b) 400 (c) 600
  33. 33.Best estimate of 781 + 532? (a) 1300 (b) 1500 (c) 1100
  34. 34.Best estimate of 151 + 307? (a) 700 (b) 500 (c) 300
  35. 35.Best estimate of 621 + 226? (a) 600 (b) 1000 (c) 800
  36. 36.Best estimate of 238 + 307? (a) 700 (b) 300 (c) 500
  37. 37.Best estimate of 20 × 89? (a) 1800 (b) 18000 (c) 180
  38. 38.Best estimate of 52 × 68? (a) 3500 (b) 35000 (c) 350
  39. 39.Best estimate of 147 + 715? (a) 600 (b) 1000 (c) 800
  40. 40.Best estimate of 97 × 21? (a) 2000 (b) 20000 (c) 200

Answer key

  1. 1600
  2. 4900
  3. 3600
  4. 1200
  5. 900
  6. 1300
  7. 8000
  8. 1100
  9. 500
  10. 1200
  11. 500
  12. 2400
  13. 7200
  14. 4500
  15. 700
  16. 1200
  17. 800
  18. 500
  19. 4200
  20. 2000
  21. 1000
  22. 2800
  23. 7200
  24. 5400
  25. 1100
  26. 2800
  27. 900
  28. 800
  29. 5400
  30. 1000
  31. 700
  32. 400
  33. 1300
  34. 500
  35. 800
  36. 500
  37. 1800
  38. 3500
  39. 800
  40. 2000

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