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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 29 · 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 272 + 347? (a) 800 (b) 400 (c) 600
  2. 2.Best estimate of 624 + 823? (a) 1600 (b) 1400 (c) 1200
  3. 3.Best estimate of 14 × 81? (a) 800 (b) 8000 (c) 80
  4. 4.Best estimate of 63 × 86? (a) 5400 (b) 54000 (c) 540
  5. 5.Best estimate of 16 × 43? (a) 8000 (b) 800 (c) 80
  6. 6.Best estimate of 86 × 51? (a) 450 (b) 45000 (c) 4500
  7. 7.Best estimate of 54 × 57? (a) 30000 (b) 300 (c) 3000
  8. 8.Best estimate of 32 × 39? (a) 12000 (b) 1200 (c) 120
  9. 9.Best estimate of 66 × 24? (a) 1400 (b) 14000 (c) 140
  10. 10.Best estimate of 47 × 48? (a) 250 (b) 2500 (c) 25000
  11. 11.Best estimate of 48 × 49? (a) 2500 (b) 25000 (c) 250
  12. 12.Best estimate of 671 + 611? (a) 1500 (b) 1300 (c) 1100
  13. 13.Best estimate of 434 + 168? (a) 800 (b) 600 (c) 400
  14. 14.Best estimate of 14 × 16? (a) 200 (b) 2000 (c) 20
  15. 15.Best estimate of 471 + 814? (a) 1300 (b) 1100 (c) 1500
  16. 16.Best estimate of 56 × 16? (a) 1200 (b) 12000 (c) 120
  17. 17.Best estimate of 42 × 86? (a) 36000 (b) 360 (c) 3600
  18. 18.Best estimate of 71 × 42? (a) 280 (b) 2800 (c) 28000
  19. 19.Best estimate of 31 × 74? (a) 21000 (b) 210 (c) 2100
  20. 20.Best estimate of 19 × 32? (a) 600 (b) 6000 (c) 60
  21. 21.Best estimate of 669 + 345? (a) 1000 (b) 1200 (c) 800
  22. 22.Best estimate of 183 + 124? (a) 500 (b) 300 (c) 100
  23. 23.Best estimate of 23 × 16? (a) 40 (b) 400 (c) 4000
  24. 24.Best estimate of 20 × 46? (a) 1000 (b) 100 (c) 10000
  25. 25.Best estimate of 31 × 27? (a) 90 (b) 900 (c) 9000
  26. 26.Best estimate of 21 × 16? (a) 400 (b) 4000 (c) 40
  27. 27.Best estimate of 27 × 38? (a) 12000 (b) 120 (c) 1200
  28. 28.Best estimate of 842 + 692? (a) 1300 (b) 1500 (c) 1700
  29. 29.Best estimate of 43 × 31? (a) 12000 (b) 1200 (c) 120
  30. 30.Best estimate of 799 + 245? (a) 800 (b) 1200 (c) 1000
  31. 31.Best estimate of 31 × 54? (a) 150 (b) 15000 (c) 1500
  32. 32.Best estimate of 745 + 490? (a) 1400 (b) 1000 (c) 1200
  33. 33.Best estimate of 49 × 96? (a) 5000 (b) 50000 (c) 500
  34. 34.Best estimate of 785 + 246? (a) 800 (b) 1200 (c) 1000
  35. 35.Best estimate of 71 × 66? (a) 4900 (b) 490 (c) 49000
  36. 36.Best estimate of 78 × 86? (a) 7200 (b) 720 (c) 72000
  37. 37.Best estimate of 262 + 139? (a) 400 (b) 600 (c) 200
  38. 38.Best estimate of 88 × 51? (a) 4500 (b) 450 (c) 45000
  39. 39.Best estimate of 61 × 21? (a) 12000 (b) 1200 (c) 120
  40. 40.Best estimate of 654 + 425? (a) 1100 (b) 900 (c) 1300

Answer key

  1. 600
  2. 1400
  3. 800
  4. 5400
  5. 800
  6. 4500
  7. 3000
  8. 1200
  9. 1400
  10. 2500
  11. 2500
  12. 1300
  13. 600
  14. 200
  15. 1300
  16. 1200
  17. 3600
  18. 2800
  19. 2100
  20. 600
  21. 1000
  22. 300
  23. 400
  24. 1000
  25. 900
  26. 400
  27. 1200
  28. 1500
  29. 1200
  30. 1000
  31. 1500
  32. 1200
  33. 5000
  34. 1000
  35. 4900
  36. 7200
  37. 400
  38. 4500
  39. 1200
  40. 1100

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