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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 859 · 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 18 × 42? (a) 80 (b) 800 (c) 8000
  2. 2.Best estimate of 50 × 66? (a) 350 (b) 35000 (c) 3500
  3. 3.Best estimate of 14 × 34? (a) 30 (b) 3000 (c) 300
  4. 4.Best estimate of 32 × 12? (a) 300 (b) 3000 (c) 30
  5. 5.Best estimate of 81 × 13? (a) 8000 (b) 800 (c) 80
  6. 6.Best estimate of 36 × 22? (a) 800 (b) 8000 (c) 80
  7. 7.Best estimate of 428 + 477? (a) 1100 (b) 700 (c) 900
  8. 8.Best estimate of 50 × 22? (a) 10000 (b) 1000 (c) 100
  9. 9.Best estimate of 238 + 128? (a) 100 (b) 300 (c) 500
  10. 10.Best estimate of 16 × 62? (a) 120 (b) 1200 (c) 12000
  11. 11.Best estimate of 62 × 87? (a) 5400 (b) 540 (c) 54000
  12. 12.Best estimate of 615 + 259? (a) 900 (b) 700 (c) 1100
  13. 13.Best estimate of 700 + 168? (a) 1100 (b) 700 (c) 900
  14. 14.Best estimate of 811 + 728? (a) 1300 (b) 1500 (c) 1700
  15. 15.Best estimate of 12 × 29? (a) 300 (b) 30 (c) 3000
  16. 16.Best estimate of 80 × 26? (a) 2400 (b) 240 (c) 24000
  17. 17.Best estimate of 78 × 23? (a) 16000 (b) 1600 (c) 160
  18. 18.Best estimate of 22 × 84? (a) 160 (b) 1600 (c) 16000
  19. 19.Best estimate of 16 × 42? (a) 8000 (b) 800 (c) 80
  20. 20.Best estimate of 123 + 330? (a) 200 (b) 600 (c) 400
  21. 21.Best estimate of 20 × 19? (a) 4000 (b) 40 (c) 400
  22. 22.Best estimate of 62 × 23? (a) 12000 (b) 120 (c) 1200
  23. 23.Best estimate of 133 + 521? (a) 600 (b) 800 (c) 400
  24. 24.Best estimate of 733 + 329? (a) 1000 (b) 1200 (c) 800
  25. 25.Best estimate of 37 × 92? (a) 360 (b) 36000 (c) 3600
  26. 26.Best estimate of 217 + 537? (a) 700 (b) 900 (c) 500
  27. 27.Best estimate of 774 + 211? (a) 1000 (b) 1200 (c) 800
  28. 28.Best estimate of 152 + 185? (a) 400 (b) 600 (c) 200
  29. 29.Best estimate of 203 + 682? (a) 900 (b) 1100 (c) 700
  30. 30.Best estimate of 24 × 12? (a) 20 (b) 200 (c) 2000
  31. 31.Best estimate of 80 × 38? (a) 3200 (b) 32000 (c) 320
  32. 32.Best estimate of 54 × 79? (a) 40000 (b) 400 (c) 4000
  33. 33.Best estimate of 76 × 27? (a) 2400 (b) 240 (c) 24000
  34. 34.Best estimate of 799 + 208? (a) 1000 (b) 800 (c) 1200
  35. 35.Best estimate of 186 + 718? (a) 900 (b) 700 (c) 1100
  36. 36.Best estimate of 80 × 13? (a) 800 (b) 80 (c) 8000
  37. 37.Best estimate of 691 + 170? (a) 900 (b) 700 (c) 1100
  38. 38.Best estimate of 769 + 854? (a) 1900 (b) 1500 (c) 1700
  39. 39.Best estimate of 28 × 88? (a) 2700 (b) 27000 (c) 270
  40. 40.Best estimate of 751 + 716? (a) 1500 (b) 1700 (c) 1300

Answer key

  1. 800
  2. 3500
  3. 300
  4. 300
  5. 800
  6. 800
  7. 900
  8. 1000
  9. 300
  10. 1200
  11. 5400
  12. 900
  13. 900
  14. 1500
  15. 300
  16. 2400
  17. 1600
  18. 1600
  19. 800
  20. 400
  21. 400
  22. 1200
  23. 600
  24. 1000
  25. 3600
  26. 700
  27. 1000
  28. 400
  29. 900
  30. 200
  31. 3200
  32. 4000
  33. 2400
  34. 1000
  35. 900
  36. 800
  37. 900
  38. 1700
  39. 2700
  40. 1500

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