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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 425 · 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 79 × 86? (a) 7200 (b) 72000 (c) 720
  2. 2.Best estimate of 49 × 68? (a) 35000 (b) 350 (c) 3500
  3. 3.Best estimate of 24 × 39? (a) 8000 (b) 800 (c) 80
  4. 4.Best estimate of 770 + 159? (a) 1000 (b) 1200 (c) 800
  5. 5.Best estimate of 82 × 89? (a) 7200 (b) 720 (c) 72000
  6. 6.Best estimate of 391 + 520? (a) 900 (b) 700 (c) 1100
  7. 7.Best estimate of 42 × 26? (a) 1200 (b) 120 (c) 12000
  8. 8.Best estimate of 74 × 83? (a) 56000 (b) 5600 (c) 560
  9. 9.Best estimate of 73 × 79? (a) 5600 (b) 56000 (c) 560
  10. 10.Best estimate of 33 × 46? (a) 1500 (b) 150 (c) 15000
  11. 11.Best estimate of 48 × 79? (a) 400 (b) 4000 (c) 40000
  12. 12.Best estimate of 639 + 302? (a) 900 (b) 700 (c) 1100
  13. 13.Best estimate of 73 × 34? (a) 210 (b) 21000 (c) 2100
  14. 14.Best estimate of 22 × 89? (a) 1800 (b) 180 (c) 18000
  15. 15.Best estimate of 353 + 407? (a) 1000 (b) 600 (c) 800
  16. 16.Best estimate of 78 × 17? (a) 16000 (b) 1600 (c) 160
  17. 17.Best estimate of 751 + 715? (a) 1300 (b) 1700 (c) 1500
  18. 18.Best estimate of 19 × 97? (a) 200 (b) 20000 (c) 2000
  19. 19.Best estimate of 686 + 413? (a) 900 (b) 1300 (c) 1100
  20. 20.Best estimate of 16 × 58? (a) 12000 (b) 1200 (c) 120
  21. 21.Best estimate of 24 × 52? (a) 10000 (b) 100 (c) 1000
  22. 22.Best estimate of 21 × 61? (a) 1200 (b) 120 (c) 12000
  23. 23.Best estimate of 165 + 192? (a) 200 (b) 600 (c) 400
  24. 24.Best estimate of 833 + 316? (a) 1100 (b) 1300 (c) 900
  25. 25.Best estimate of 139 + 244? (a) 300 (b) 500 (c) 100
  26. 26.Best estimate of 34 × 84? (a) 2400 (b) 240 (c) 24000
  27. 27.Best estimate of 66 × 56? (a) 42000 (b) 4200 (c) 420
  28. 28.Best estimate of 51 × 90? (a) 450 (b) 45000 (c) 4500
  29. 29.Best estimate of 31 × 41? (a) 1200 (b) 120 (c) 12000
  30. 30.Best estimate of 333 + 312? (a) 400 (b) 800 (c) 600
  31. 31.Best estimate of 40 × 44? (a) 1600 (b) 16000 (c) 160
  32. 32.Best estimate of 651 + 536? (a) 1400 (b) 1000 (c) 1200
  33. 33.Best estimate of 553 + 647? (a) 1400 (b) 1200 (c) 1000
  34. 34.Best estimate of 235 + 694? (a) 1100 (b) 900 (c) 700
  35. 35.Best estimate of 68 × 19? (a) 14000 (b) 1400 (c) 140
  36. 36.Best estimate of 56 × 13? (a) 6000 (b) 60 (c) 600
  37. 37.Best estimate of 866 + 186? (a) 1100 (b) 1300 (c) 900
  38. 38.Best estimate of 92 × 28? (a) 2700 (b) 270 (c) 27000
  39. 39.Best estimate of 58 × 86? (a) 540 (b) 54000 (c) 5400
  40. 40.Best estimate of 29 × 24? (a) 60 (b) 600 (c) 6000

Answer key

  1. 7200
  2. 3500
  3. 800
  4. 1000
  5. 7200
  6. 900
  7. 1200
  8. 5600
  9. 5600
  10. 1500
  11. 4000
  12. 900
  13. 2100
  14. 1800
  15. 800
  16. 1600
  17. 1500
  18. 2000
  19. 1100
  20. 1200
  21. 1000
  22. 1200
  23. 400
  24. 1100
  25. 300
  26. 2400
  27. 4200
  28. 4500
  29. 1200
  30. 600
  31. 1600
  32. 1200
  33. 1200
  34. 900
  35. 1400
  36. 600
  37. 1100
  38. 2700
  39. 5400
  40. 600

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