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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 45 · 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 54 × 34? (a) 15000 (b) 1500 (c) 150
  2. 2.Best estimate of 128 + 552? (a) 700 (b) 900 (c) 500
  3. 3.Best estimate of 615 + 482? (a) 900 (b) 1100 (c) 1300
  4. 4.Best estimate of 58 × 60? (a) 3600 (b) 36000 (c) 360
  5. 5.Best estimate of 43 × 89? (a) 36000 (b) 3600 (c) 360
  6. 6.Best estimate of 289 + 168? (a) 700 (b) 500 (c) 300
  7. 7.Best estimate of 706 + 632? (a) 1300 (b) 1500 (c) 1100
  8. 8.Best estimate of 16 × 48? (a) 1000 (b) 100 (c) 10000
  9. 9.Best estimate of 555 + 504? (a) 1100 (b) 1300 (c) 900
  10. 10.Best estimate of 56 × 34? (a) 18000 (b) 1800 (c) 180
  11. 11.Best estimate of 98 × 80? (a) 8000 (b) 80000 (c) 800
  12. 12.Best estimate of 72 × 31? (a) 2100 (b) 21000 (c) 210
  13. 13.Best estimate of 26 × 72? (a) 2100 (b) 21000 (c) 210
  14. 14.Best estimate of 27 × 89? (a) 27000 (b) 2700 (c) 270
  15. 15.Best estimate of 26 × 61? (a) 1800 (b) 18000 (c) 180
  16. 16.Best estimate of 382 + 654? (a) 1100 (b) 900 (c) 1300
  17. 17.Best estimate of 24 × 71? (a) 140 (b) 14000 (c) 1400
  18. 18.Best estimate of 283 + 574? (a) 1100 (b) 700 (c) 900
  19. 19.Best estimate of 79 × 37? (a) 3200 (b) 32000 (c) 320
  20. 20.Best estimate of 66 × 96? (a) 70000 (b) 700 (c) 7000
  21. 21.Best estimate of 88 × 20? (a) 18000 (b) 1800 (c) 180
  22. 22.Best estimate of 202 + 824? (a) 800 (b) 1200 (c) 1000
  23. 23.Best estimate of 57 × 14? (a) 600 (b) 6000 (c) 60
  24. 24.Best estimate of 521 + 152? (a) 900 (b) 500 (c) 700
  25. 25.Best estimate of 303 + 189? (a) 700 (b) 500 (c) 300
  26. 26.Best estimate of 77 × 13? (a) 8000 (b) 800 (c) 80
  27. 27.Best estimate of 16 × 40? (a) 80 (b) 800 (c) 8000
  28. 28.Best estimate of 564 + 422? (a) 800 (b) 1200 (c) 1000
  29. 29.Best estimate of 26 × 34? (a) 900 (b) 9000 (c) 90
  30. 30.Best estimate of 327 + 207? (a) 700 (b) 500 (c) 300
  31. 31.Best estimate of 49 × 64? (a) 30000 (b) 300 (c) 3000
  32. 32.Best estimate of 36 × 80? (a) 320 (b) 32000 (c) 3200
  33. 33.Best estimate of 492 + 240? (a) 900 (b) 500 (c) 700
  34. 34.Best estimate of 677 + 729? (a) 1400 (b) 1200 (c) 1600
  35. 35.Best estimate of 48 × 14? (a) 5000 (b) 50 (c) 500
  36. 36.Best estimate of 702 + 654? (a) 1200 (b) 1400 (c) 1600
  37. 37.Best estimate of 388 + 547? (a) 1100 (b) 900 (c) 700
  38. 38.Best estimate of 699 + 243? (a) 900 (b) 1100 (c) 700
  39. 39.Best estimate of 44 × 31? (a) 120 (b) 12000 (c) 1200
  40. 40.Best estimate of 683 + 836? (a) 1700 (b) 1300 (c) 1500

Answer key

  1. 1500
  2. 700
  3. 1100
  4. 3600
  5. 3600
  6. 500
  7. 1300
  8. 1000
  9. 1100
  10. 1800
  11. 8000
  12. 2100
  13. 2100
  14. 2700
  15. 1800
  16. 1100
  17. 1400
  18. 900
  19. 3200
  20. 7000
  21. 1800
  22. 1000
  23. 600
  24. 700
  25. 500
  26. 800
  27. 800
  28. 1000
  29. 900
  30. 500
  31. 3000
  32. 3200
  33. 700
  34. 1400
  35. 500
  36. 1400
  37. 900
  38. 900
  39. 1200
  40. 1500

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