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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 100 · 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 810 + 193? (a) 800 (b) 1200 (c) 1000
  2. 2.Best estimate of 36 × 20? (a) 80 (b) 8000 (c) 800
  3. 3.Best estimate of 52 × 23? (a) 10000 (b) 1000 (c) 100
  4. 4.Best estimate of 418 + 249? (a) 600 (b) 400 (c) 800
  5. 5.Best estimate of 254 + 810? (a) 1100 (b) 1300 (c) 900
  6. 6.Best estimate of 490 + 136? (a) 600 (b) 400 (c) 800
  7. 7.Best estimate of 541 + 515? (a) 1000 (b) 1200 (c) 800
  8. 8.Best estimate of 92 × 12? (a) 9000 (b) 90 (c) 900
  9. 9.Best estimate of 390 + 565? (a) 800 (b) 1000 (c) 1200
  10. 10.Best estimate of 94 × 47? (a) 450 (b) 45000 (c) 4500
  11. 11.Best estimate of 66 × 57? (a) 4200 (b) 42000 (c) 420
  12. 12.Best estimate of 54 × 13? (a) 500 (b) 5000 (c) 50
  13. 13.Best estimate of 22 × 60? (a) 1200 (b) 120 (c) 12000
  14. 14.Best estimate of 38 × 36? (a) 16000 (b) 1600 (c) 160
  15. 15.Best estimate of 16 × 56? (a) 12000 (b) 1200 (c) 120
  16. 16.Best estimate of 66 × 62? (a) 4200 (b) 42000 (c) 420
  17. 17.Best estimate of 97 × 19? (a) 2000 (b) 200 (c) 20000
  18. 18.Best estimate of 747 + 796? (a) 1700 (b) 1300 (c) 1500
  19. 19.Best estimate of 87 × 83? (a) 7200 (b) 72000 (c) 720
  20. 20.Best estimate of 464 + 366? (a) 900 (b) 1100 (c) 700
  21. 21.Best estimate of 554 + 351? (a) 800 (b) 1000 (c) 1200
  22. 22.Best estimate of 230 + 166? (a) 400 (b) 200 (c) 600
  23. 23.Best estimate of 836 + 410? (a) 1400 (b) 1000 (c) 1200
  24. 24.Best estimate of 66 × 94? (a) 630 (b) 6300 (c) 63000
  25. 25.Best estimate of 48 × 36? (a) 20000 (b) 2000 (c) 200
  26. 26.Best estimate of 73 × 56? (a) 42000 (b) 4200 (c) 420
  27. 27.Best estimate of 851 + 388? (a) 1100 (b) 1500 (c) 1300
  28. 28.Best estimate of 599 + 301? (a) 1100 (b) 900 (c) 700
  29. 29.Best estimate of 96 × 36? (a) 4000 (b) 400 (c) 40000
  30. 30.Best estimate of 457 + 139? (a) 400 (b) 800 (c) 600
  31. 31.Best estimate of 51 × 71? (a) 35000 (b) 3500 (c) 350
  32. 32.Best estimate of 165 + 162? (a) 200 (b) 600 (c) 400
  33. 33.Best estimate of 97 × 16? (a) 200 (b) 2000 (c) 20000
  34. 34.Best estimate of 38 × 79? (a) 320 (b) 3200 (c) 32000
  35. 35.Best estimate of 51 × 12? (a) 500 (b) 50 (c) 5000
  36. 36.Best estimate of 98 × 57? (a) 6000 (b) 600 (c) 60000
  37. 37.Best estimate of 97 × 31? (a) 30000 (b) 3000 (c) 300
  38. 38.Best estimate of 24 × 62? (a) 120 (b) 1200 (c) 12000
  39. 39.Best estimate of 403 + 449? (a) 600 (b) 800 (c) 1000
  40. 40.Best estimate of 671 + 326? (a) 1200 (b) 1000 (c) 800

Answer key

  1. 1000
  2. 800
  3. 1000
  4. 600
  5. 1100
  6. 600
  7. 1000
  8. 900
  9. 1000
  10. 4500
  11. 4200
  12. 500
  13. 1200
  14. 1600
  15. 1200
  16. 4200
  17. 2000
  18. 1500
  19. 7200
  20. 900
  21. 1000
  22. 400
  23. 1200
  24. 6300
  25. 2000
  26. 4200
  27. 1300
  28. 900
  29. 4000
  30. 600
  31. 3500
  32. 400
  33. 2000
  34. 3200
  35. 500
  36. 6000
  37. 3000
  38. 1200
  39. 800
  40. 1000

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