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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 85 · 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 149 + 158? (a) 100 (b) 500 (c) 300
  2. 2.Best estimate of 86 × 96? (a) 90000 (b) 900 (c) 9000
  3. 3.Best estimate of 640 + 836? (a) 1200 (b) 1400 (c) 1600
  4. 4.Best estimate of 26 × 91? (a) 27000 (b) 2700 (c) 270
  5. 5.Best estimate of 91 × 20? (a) 1800 (b) 180 (c) 18000
  6. 6.Best estimate of 502 + 492? (a) 1200 (b) 1000 (c) 800
  7. 7.Best estimate of 374 + 138? (a) 300 (b) 500 (c) 700
  8. 8.Best estimate of 762 + 230? (a) 800 (b) 1000 (c) 1200
  9. 9.Best estimate of 737 + 739? (a) 1600 (b) 1200 (c) 1400
  10. 10.Best estimate of 481 + 193? (a) 900 (b) 500 (c) 700
  11. 11.Best estimate of 810 + 318? (a) 1300 (b) 900 (c) 1100
  12. 12.Best estimate of 24 × 36? (a) 800 (b) 80 (c) 8000
  13. 13.Best estimate of 26 × 72? (a) 21000 (b) 210 (c) 2100
  14. 14.Best estimate of 67 × 50? (a) 350 (b) 35000 (c) 3500
  15. 15.Best estimate of 98 × 72? (a) 7000 (b) 700 (c) 70000
  16. 16.Best estimate of 56 × 38? (a) 2400 (b) 24000 (c) 240
  17. 17.Best estimate of 725 + 209? (a) 1100 (b) 700 (c) 900
  18. 18.Best estimate of 72 × 16? (a) 1400 (b) 14000 (c) 140
  19. 19.Best estimate of 176 + 367? (a) 600 (b) 400 (c) 800
  20. 20.Best estimate of 490 + 809? (a) 1300 (b) 1100 (c) 1500
  21. 21.Best estimate of 96 × 86? (a) 900 (b) 90000 (c) 9000
  22. 22.Best estimate of 189 + 409? (a) 400 (b) 600 (c) 800
  23. 23.Best estimate of 317 + 285? (a) 800 (b) 400 (c) 600
  24. 24.Best estimate of 56 × 50? (a) 3000 (b) 30000 (c) 300
  25. 25.Best estimate of 219 + 332? (a) 500 (b) 700 (c) 300
  26. 26.Best estimate of 296 + 378? (a) 700 (b) 500 (c) 900
  27. 27.Best estimate of 61 × 90? (a) 54000 (b) 5400 (c) 540
  28. 28.Best estimate of 229 + 206? (a) 600 (b) 400 (c) 200
  29. 29.Best estimate of 327 + 631? (a) 1100 (b) 700 (c) 900
  30. 30.Best estimate of 318 + 204? (a) 700 (b) 500 (c) 300
  31. 31.Best estimate of 87 × 47? (a) 450 (b) 45000 (c) 4500
  32. 32.Best estimate of 69 × 71? (a) 49000 (b) 4900 (c) 490
  33. 33.Best estimate of 66 × 16? (a) 140 (b) 1400 (c) 14000
  34. 34.Best estimate of 468 + 363? (a) 1100 (b) 900 (c) 700
  35. 35.Best estimate of 33 × 96? (a) 300 (b) 3000 (c) 30000
  36. 36.Best estimate of 24 × 66? (a) 1400 (b) 14000 (c) 140
  37. 37.Best estimate of 84 × 97? (a) 8000 (b) 80000 (c) 800
  38. 38.Best estimate of 461 + 636? (a) 900 (b) 1300 (c) 1100
  39. 39.Best estimate of 82 × 13? (a) 800 (b) 80 (c) 8000
  40. 40.Best estimate of 591 + 431? (a) 1200 (b) 1000 (c) 800

Answer key

  1. 300
  2. 9000
  3. 1400
  4. 2700
  5. 1800
  6. 1000
  7. 500
  8. 1000
  9. 1400
  10. 700
  11. 1100
  12. 800
  13. 2100
  14. 3500
  15. 7000
  16. 2400
  17. 900
  18. 1400
  19. 600
  20. 1300
  21. 9000
  22. 600
  23. 600
  24. 3000
  25. 500
  26. 700
  27. 5400
  28. 400
  29. 900
  30. 500
  31. 4500
  32. 4900
  33. 1400
  34. 900
  35. 3000
  36. 1400
  37. 8000
  38. 1100
  39. 800
  40. 1000

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