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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 266 · 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 423 + 628? (a) 800 (b) 1000 (c) 1200
  2. 2.Best estimate of 771 + 340? (a) 1100 (b) 900 (c) 1300
  3. 3.Best estimate of 339 + 193? (a) 500 (b) 300 (c) 700
  4. 4.Best estimate of 266 + 760? (a) 1100 (b) 1300 (c) 900
  5. 5.Best estimate of 77 × 30? (a) 24000 (b) 240 (c) 2400
  6. 6.Best estimate of 618 + 415? (a) 800 (b) 1200 (c) 1000
  7. 7.Best estimate of 94 × 26? (a) 27000 (b) 270 (c) 2700
  8. 8.Best estimate of 46 × 89? (a) 45000 (b) 4500 (c) 450
  9. 9.Best estimate of 83 × 91? (a) 720 (b) 7200 (c) 72000
  10. 10.Best estimate of 558 + 161? (a) 800 (b) 600 (c) 1000
  11. 11.Best estimate of 167 + 231? (a) 400 (b) 200 (c) 600
  12. 12.Best estimate of 251 + 663? (a) 800 (b) 1200 (c) 1000
  13. 13.Best estimate of 206 + 616? (a) 1000 (b) 800 (c) 600
  14. 14.Best estimate of 26 × 46? (a) 150 (b) 15000 (c) 1500
  15. 15.Best estimate of 23 × 33? (a) 60 (b) 600 (c) 6000
  16. 16.Best estimate of 28 × 88? (a) 27000 (b) 270 (c) 2700
  17. 17.Best estimate of 21 × 86? (a) 180 (b) 1800 (c) 18000
  18. 18.Best estimate of 339 + 205? (a) 700 (b) 300 (c) 500
  19. 19.Best estimate of 21 × 51? (a) 10000 (b) 1000 (c) 100
  20. 20.Best estimate of 744 + 375? (a) 1300 (b) 900 (c) 1100
  21. 21.Best estimate of 786 + 645? (a) 1600 (b) 1400 (c) 1200
  22. 22.Best estimate of 34 × 43? (a) 12000 (b) 1200 (c) 120
  23. 23.Best estimate of 290 + 292? (a) 400 (b) 800 (c) 600
  24. 24.Best estimate of 16 × 19? (a) 400 (b) 40 (c) 4000
  25. 25.Best estimate of 646 + 292? (a) 900 (b) 700 (c) 1100
  26. 26.Best estimate of 36 × 30? (a) 12000 (b) 120 (c) 1200
  27. 27.Best estimate of 96 × 92? (a) 9000 (b) 900 (c) 90000
  28. 28.Best estimate of 49 × 18? (a) 10000 (b) 100 (c) 1000
  29. 29.Best estimate of 48 × 13? (a) 500 (b) 50 (c) 5000
  30. 30.Best estimate of 64 × 53? (a) 3000 (b) 30000 (c) 300
  31. 31.Best estimate of 863 + 431? (a) 1100 (b) 1300 (c) 1500
  32. 32.Best estimate of 449 + 281? (a) 900 (b) 700 (c) 500
  33. 33.Best estimate of 56 × 17? (a) 1200 (b) 12000 (c) 120
  34. 34.Best estimate of 704 + 243? (a) 700 (b) 900 (c) 1100
  35. 35.Best estimate of 72 × 14? (a) 7000 (b) 700 (c) 70
  36. 36.Best estimate of 30 × 13? (a) 300 (b) 30 (c) 3000
  37. 37.Best estimate of 787 + 293? (a) 1300 (b) 900 (c) 1100
  38. 38.Best estimate of 276 + 261? (a) 400 (b) 600 (c) 800
  39. 39.Best estimate of 30 × 27? (a) 90 (b) 900 (c) 9000
  40. 40.Best estimate of 98 × 73? (a) 7000 (b) 70000 (c) 700

Answer key

  1. 1000
  2. 1100
  3. 500
  4. 1100
  5. 2400
  6. 1000
  7. 2700
  8. 4500
  9. 7200
  10. 800
  11. 400
  12. 1000
  13. 800
  14. 1500
  15. 600
  16. 2700
  17. 1800
  18. 500
  19. 1000
  20. 1100
  21. 1400
  22. 1200
  23. 600
  24. 400
  25. 900
  26. 1200
  27. 9000
  28. 1000
  29. 500
  30. 3000
  31. 1300
  32. 700
  33. 1200
  34. 900
  35. 700
  36. 300
  37. 1100
  38. 600
  39. 900
  40. 7000

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