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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 804 · 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 70 × 67? (a) 4900 (b) 490 (c) 49000
  2. 2.Best estimate of 22 × 43? (a) 800 (b) 8000 (c) 80
  3. 3.Best estimate of 66 × 42? (a) 280 (b) 2800 (c) 28000
  4. 4.Best estimate of 56 × 72? (a) 4200 (b) 420 (c) 42000
  5. 5.Best estimate of 98 × 96? (a) 1000 (b) 10000 (c) 100000
  6. 6.Best estimate of 36 × 26? (a) 120 (b) 12000 (c) 1200
  7. 7.Best estimate of 54 × 92? (a) 45000 (b) 4500 (c) 450
  8. 8.Best estimate of 40 × 23? (a) 800 (b) 8000 (c) 80
  9. 9.Best estimate of 22 × 27? (a) 60 (b) 600 (c) 6000
  10. 10.Best estimate of 571 + 519? (a) 1100 (b) 900 (c) 1300
  11. 11.Best estimate of 76 × 66? (a) 5600 (b) 56000 (c) 560
  12. 12.Best estimate of 293 + 648? (a) 700 (b) 900 (c) 1100
  13. 13.Best estimate of 33 × 90? (a) 270 (b) 27000 (c) 2700
  14. 14.Best estimate of 49 × 79? (a) 400 (b) 40000 (c) 4000
  15. 15.Best estimate of 626 + 278? (a) 900 (b) 700 (c) 1100
  16. 16.Best estimate of 161 + 644? (a) 1000 (b) 600 (c) 800
  17. 17.Best estimate of 366 + 732? (a) 1100 (b) 1300 (c) 900
  18. 18.Best estimate of 155 + 528? (a) 500 (b) 900 (c) 700
  19. 19.Best estimate of 78 × 87? (a) 720 (b) 72000 (c) 7200
  20. 20.Best estimate of 38 × 57? (a) 24000 (b) 2400 (c) 240
  21. 21.Best estimate of 149 + 142? (a) 400 (b) 200 (c) 0
  22. 22.Best estimate of 33 × 86? (a) 2700 (b) 270 (c) 27000
  23. 23.Best estimate of 80 × 71? (a) 56000 (b) 560 (c) 5600
  24. 24.Best estimate of 830 + 253? (a) 1300 (b) 900 (c) 1100
  25. 25.Best estimate of 240 + 141? (a) 300 (b) 100 (c) 500
  26. 26.Best estimate of 59 × 51? (a) 30000 (b) 300 (c) 3000
  27. 27.Best estimate of 73 × 56? (a) 4200 (b) 420 (c) 42000
  28. 28.Best estimate of 240 + 702? (a) 700 (b) 1100 (c) 900
  29. 29.Best estimate of 46 × 23? (a) 10000 (b) 1000 (c) 100
  30. 30.Best estimate of 21 × 70? (a) 14000 (b) 1400 (c) 140
  31. 31.Best estimate of 549 + 122? (a) 600 (b) 400 (c) 800
  32. 32.Best estimate of 668 + 203? (a) 1100 (b) 900 (c) 700
  33. 33.Best estimate of 234 + 240? (a) 200 (b) 600 (c) 400
  34. 34.Best estimate of 36 × 88? (a) 3600 (b) 360 (c) 36000
  35. 35.Best estimate of 308 + 639? (a) 1100 (b) 900 (c) 700
  36. 36.Best estimate of 62 × 26? (a) 180 (b) 18000 (c) 1800
  37. 37.Best estimate of 378 + 439? (a) 800 (b) 600 (c) 1000
  38. 38.Best estimate of 74 × 21? (a) 14000 (b) 1400 (c) 140
  39. 39.Best estimate of 82 × 33? (a) 24000 (b) 2400 (c) 240
  40. 40.Best estimate of 46 × 36? (a) 2000 (b) 20000 (c) 200

Answer key

  1. 4900
  2. 800
  3. 2800
  4. 4200
  5. 10000
  6. 1200
  7. 4500
  8. 800
  9. 600
  10. 1100
  11. 5600
  12. 900
  13. 2700
  14. 4000
  15. 900
  16. 800
  17. 1100
  18. 700
  19. 7200
  20. 2400
  21. 200
  22. 2700
  23. 5600
  24. 1100
  25. 300
  26. 3000
  27. 4200
  28. 900
  29. 1000
  30. 1400
  31. 600
  32. 900
  33. 400
  34. 3600
  35. 900
  36. 1800
  37. 800
  38. 1400
  39. 2400
  40. 2000

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