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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 159 · 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 × 70? (a) 140 (b) 14000 (c) 1400
  2. 2.Best estimate of 539 + 845? (a) 1300 (b) 1500 (c) 1100
  3. 3.Best estimate of 87 × 14? (a) 9000 (b) 900 (c) 90
  4. 4.Best estimate of 77 × 79? (a) 64000 (b) 6400 (c) 640
  5. 5.Best estimate of 690 + 376? (a) 900 (b) 1100 (c) 1300
  6. 6.Best estimate of 72 × 86? (a) 630 (b) 63000 (c) 6300
  7. 7.Best estimate of 21 × 86? (a) 18000 (b) 180 (c) 1800
  8. 8.Best estimate of 40 × 20? (a) 800 (b) 8000 (c) 80
  9. 9.Best estimate of 649 + 409? (a) 1000 (b) 800 (c) 1200
  10. 10.Best estimate of 76 × 81? (a) 640 (b) 64000 (c) 6400
  11. 11.Best estimate of 606 + 182? (a) 1000 (b) 800 (c) 600
  12. 12.Best estimate of 80 × 28? (a) 24000 (b) 240 (c) 2400
  13. 13.Best estimate of 91 × 92? (a) 810 (b) 81000 (c) 8100
  14. 14.Best estimate of 486 + 465? (a) 1000 (b) 1200 (c) 800
  15. 15.Best estimate of 359 + 873? (a) 1100 (b) 1300 (c) 1500
  16. 16.Best estimate of 238 + 442? (a) 800 (b) 400 (c) 600
  17. 17.Best estimate of 89 × 37? (a) 36000 (b) 3600 (c) 360
  18. 18.Best estimate of 335 + 776? (a) 1100 (b) 1300 (c) 900
  19. 19.Best estimate of 56 × 84? (a) 48000 (b) 4800 (c) 480
  20. 20.Best estimate of 173 + 155? (a) 400 (b) 600 (c) 200
  21. 21.Best estimate of 12 × 34? (a) 30 (b) 3000 (c) 300
  22. 22.Best estimate of 214 + 279? (a) 700 (b) 500 (c) 300
  23. 23.Best estimate of 34 × 40? (a) 1200 (b) 12000 (c) 120
  24. 24.Best estimate of 643 + 196? (a) 600 (b) 800 (c) 1000
  25. 25.Best estimate of 66 × 32? (a) 2100 (b) 210 (c) 21000
  26. 26.Best estimate of 56 × 71? (a) 4200 (b) 420 (c) 42000
  27. 27.Best estimate of 279 + 437? (a) 900 (b) 500 (c) 700
  28. 28.Best estimate of 27 × 22? (a) 6000 (b) 60 (c) 600
  29. 29.Best estimate of 70 × 73? (a) 4900 (b) 490 (c) 49000
  30. 30.Best estimate of 80 × 23? (a) 16000 (b) 160 (c) 1600
  31. 31.Best estimate of 44 × 52? (a) 20000 (b) 2000 (c) 200
  32. 32.Best estimate of 566 + 734? (a) 1100 (b) 1500 (c) 1300
  33. 33.Best estimate of 669 + 834? (a) 1300 (b) 1500 (c) 1700
  34. 34.Best estimate of 63 × 19? (a) 120 (b) 12000 (c) 1200
  35. 35.Best estimate of 44 × 89? (a) 3600 (b) 360 (c) 36000
  36. 36.Best estimate of 92 × 86? (a) 81000 (b) 810 (c) 8100
  37. 37.Best estimate of 90 × 77? (a) 7200 (b) 72000 (c) 720
  38. 38.Best estimate of 94 × 82? (a) 72000 (b) 7200 (c) 720
  39. 39.Best estimate of 56 × 90? (a) 54000 (b) 540 (c) 5400
  40. 40.Best estimate of 580 + 120? (a) 500 (b) 900 (c) 700

Answer key

  1. 1400
  2. 1300
  3. 900
  4. 6400
  5. 1100
  6. 6300
  7. 1800
  8. 800
  9. 1000
  10. 6400
  11. 800
  12. 2400
  13. 8100
  14. 1000
  15. 1300
  16. 600
  17. 3600
  18. 1100
  19. 4800
  20. 400
  21. 300
  22. 500
  23. 1200
  24. 800
  25. 2100
  26. 4200
  27. 700
  28. 600
  29. 4900
  30. 1600
  31. 2000
  32. 1300
  33. 1500
  34. 1200
  35. 3600
  36. 8100
  37. 7200
  38. 7200
  39. 5400
  40. 700

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