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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 79 · 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 684 + 632? (a) 1300 (b) 1100 (c) 1500
  2. 2.Best estimate of 81 × 41? (a) 32000 (b) 3200 (c) 320
  3. 3.Best estimate of 31 × 72? (a) 2100 (b) 21000 (c) 210
  4. 4.Best estimate of 734 + 871? (a) 1600 (b) 1800 (c) 1400
  5. 5.Best estimate of 589 + 456? (a) 1100 (b) 900 (c) 1300
  6. 6.Best estimate of 73 × 34? (a) 2100 (b) 210 (c) 21000
  7. 7.Best estimate of 222 + 147? (a) 100 (b) 300 (c) 500
  8. 8.Best estimate of 59 × 49? (a) 3000 (b) 30000 (c) 300
  9. 9.Best estimate of 414 + 414? (a) 1000 (b) 800 (c) 600
  10. 10.Best estimate of 770 + 789? (a) 1600 (b) 1800 (c) 1400
  11. 11.Best estimate of 89 × 39? (a) 36000 (b) 3600 (c) 360
  12. 12.Best estimate of 62 × 78? (a) 4800 (b) 480 (c) 48000
  13. 13.Best estimate of 762 + 125? (a) 900 (b) 700 (c) 1100
  14. 14.Best estimate of 26 × 57? (a) 18000 (b) 1800 (c) 180
  15. 15.Best estimate of 80 × 53? (a) 400 (b) 40000 (c) 4000
  16. 16.Best estimate of 26 × 42? (a) 120 (b) 12000 (c) 1200
  17. 17.Best estimate of 541 + 211? (a) 900 (b) 700 (c) 500
  18. 18.Best estimate of 783 + 696? (a) 1300 (b) 1500 (c) 1700
  19. 19.Best estimate of 59 × 89? (a) 54000 (b) 540 (c) 5400
  20. 20.Best estimate of 41 × 96? (a) 400 (b) 4000 (c) 40000
  21. 21.Best estimate of 20 × 20? (a) 40 (b) 400 (c) 4000
  22. 22.Best estimate of 38 × 28? (a) 12000 (b) 1200 (c) 120
  23. 23.Best estimate of 306 + 184? (a) 300 (b) 500 (c) 700
  24. 24.Best estimate of 36 × 22? (a) 8000 (b) 800 (c) 80
  25. 25.Best estimate of 351 + 779? (a) 1000 (b) 1400 (c) 1200
  26. 26.Best estimate of 44 × 13? (a) 40 (b) 400 (c) 4000
  27. 27.Best estimate of 16 × 61? (a) 120 (b) 1200 (c) 12000
  28. 28.Best estimate of 739 + 798? (a) 1500 (b) 1700 (c) 1300
  29. 29.Best estimate of 779 + 597? (a) 1200 (b) 1600 (c) 1400
  30. 30.Best estimate of 90 × 79? (a) 7200 (b) 72000 (c) 720
  31. 31.Best estimate of 335 + 148? (a) 200 (b) 400 (c) 600
  32. 32.Best estimate of 482 + 528? (a) 1000 (b) 800 (c) 1200
  33. 33.Best estimate of 31 × 21? (a) 60 (b) 600 (c) 6000
  34. 34.Best estimate of 207 + 129? (a) 500 (b) 100 (c) 300
  35. 35.Best estimate of 319 + 807? (a) 1100 (b) 1300 (c) 900
  36. 36.Best estimate of 30 × 28? (a) 900 (b) 9000 (c) 90
  37. 37.Best estimate of 231 + 532? (a) 500 (b) 900 (c) 700
  38. 38.Best estimate of 741 + 273? (a) 1000 (b) 1200 (c) 800
  39. 39.Best estimate of 19 × 32? (a) 60 (b) 600 (c) 6000
  40. 40.Best estimate of 182 + 338? (a) 700 (b) 300 (c) 500

Answer key

  1. 1300
  2. 3200
  3. 2100
  4. 1600
  5. 1100
  6. 2100
  7. 300
  8. 3000
  9. 800
  10. 1600
  11. 3600
  12. 4800
  13. 900
  14. 1800
  15. 4000
  16. 1200
  17. 700
  18. 1500
  19. 5400
  20. 4000
  21. 400
  22. 1200
  23. 500
  24. 800
  25. 1200
  26. 400
  27. 1200
  28. 1500
  29. 1400
  30. 7200
  31. 400
  32. 1000
  33. 600
  34. 300
  35. 1100
  36. 900
  37. 700
  38. 1000
  39. 600
  40. 500

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