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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 129 · 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 23 × 92? (a) 1800 (b) 180 (c) 18000
  2. 2.Best estimate of 581 + 549? (a) 900 (b) 1100 (c) 1300
  3. 3.Best estimate of 386 + 496? (a) 700 (b) 900 (c) 1100
  4. 4.Best estimate of 82 × 23? (a) 16000 (b) 160 (c) 1600
  5. 5.Best estimate of 384 + 131? (a) 700 (b) 500 (c) 300
  6. 6.Best estimate of 146 + 327? (a) 600 (b) 400 (c) 200
  7. 7.Best estimate of 742 + 630? (a) 1500 (b) 1100 (c) 1300
  8. 8.Best estimate of 89 × 54? (a) 4500 (b) 450 (c) 45000
  9. 9.Best estimate of 43 × 87? (a) 360 (b) 3600 (c) 36000
  10. 10.Best estimate of 69 × 24? (a) 1400 (b) 140 (c) 14000
  11. 11.Best estimate of 631 + 654? (a) 1500 (b) 1100 (c) 1300
  12. 12.Best estimate of 483 + 565? (a) 900 (b) 1300 (c) 1100
  13. 13.Best estimate of 522 + 165? (a) 500 (b) 700 (c) 900
  14. 14.Best estimate of 520 + 737? (a) 1200 (b) 1000 (c) 1400
  15. 15.Best estimate of 21 × 42? (a) 800 (b) 8000 (c) 80
  16. 16.Best estimate of 123 + 637? (a) 900 (b) 700 (c) 500
  17. 17.Best estimate of 94 × 84? (a) 7200 (b) 72000 (c) 720
  18. 18.Best estimate of 17 × 47? (a) 100 (b) 10000 (c) 1000
  19. 19.Best estimate of 718 + 186? (a) 700 (b) 1100 (c) 900
  20. 20.Best estimate of 862 + 737? (a) 1400 (b) 1600 (c) 1800
  21. 21.Best estimate of 77 × 58? (a) 480 (b) 4800 (c) 48000
  22. 22.Best estimate of 57 × 46? (a) 300 (b) 3000 (c) 30000
  23. 23.Best estimate of 66 × 31? (a) 21000 (b) 210 (c) 2100
  24. 24.Best estimate of 196 + 639? (a) 1000 (b) 800 (c) 600
  25. 25.Best estimate of 510 + 251? (a) 600 (b) 1000 (c) 800
  26. 26.Best estimate of 38 × 51? (a) 20000 (b) 2000 (c) 200
  27. 27.Best estimate of 28 × 42? (a) 12000 (b) 1200 (c) 120
  28. 28.Best estimate of 46 × 94? (a) 45000 (b) 4500 (c) 450
  29. 29.Best estimate of 18 × 52? (a) 100 (b) 1000 (c) 10000
  30. 30.Best estimate of 72 × 56? (a) 420 (b) 4200 (c) 42000
  31. 31.Best estimate of 60 × 29? (a) 1800 (b) 18000 (c) 180
  32. 32.Best estimate of 581 + 800? (a) 1200 (b) 1600 (c) 1400
  33. 33.Best estimate of 231 + 129? (a) 300 (b) 100 (c) 500
  34. 34.Best estimate of 96 × 90? (a) 900 (b) 90000 (c) 9000
  35. 35.Best estimate of 704 + 484? (a) 1000 (b) 1400 (c) 1200
  36. 36.Best estimate of 58 × 34? (a) 180 (b) 18000 (c) 1800
  37. 37.Best estimate of 733 + 569? (a) 1300 (b) 1500 (c) 1100
  38. 38.Best estimate of 202 + 569? (a) 600 (b) 1000 (c) 800
  39. 39.Best estimate of 31 × 49? (a) 150 (b) 1500 (c) 15000
  40. 40.Best estimate of 820 + 231? (a) 1000 (b) 1200 (c) 800

Answer key

  1. 1800
  2. 1100
  3. 900
  4. 1600
  5. 500
  6. 400
  7. 1300
  8. 4500
  9. 3600
  10. 1400
  11. 1300
  12. 1100
  13. 700
  14. 1200
  15. 800
  16. 700
  17. 7200
  18. 1000
  19. 900
  20. 1600
  21. 4800
  22. 3000
  23. 2100
  24. 800
  25. 800
  26. 2000
  27. 1200
  28. 4500
  29. 1000
  30. 4200
  31. 1800
  32. 1400
  33. 300
  34. 9000
  35. 1200
  36. 1800
  37. 1300
  38. 800
  39. 1500
  40. 1000

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