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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 138 · 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 29 × 88? (a) 270 (b) 27000 (c) 2700
  2. 2.Best estimate of 69 × 47? (a) 3500 (b) 35000 (c) 350
  3. 3.Best estimate of 73 × 28? (a) 2100 (b) 21000 (c) 210
  4. 4.Best estimate of 606 + 345? (a) 700 (b) 900 (c) 1100
  5. 5.Best estimate of 274 + 532? (a) 600 (b) 1000 (c) 800
  6. 6.Best estimate of 16 × 76? (a) 1600 (b) 160 (c) 16000
  7. 7.Best estimate of 92 × 26? (a) 2700 (b) 27000 (c) 270
  8. 8.Best estimate of 82 × 31? (a) 2400 (b) 24000 (c) 240
  9. 9.Best estimate of 280 + 301? (a) 600 (b) 400 (c) 800
  10. 10.Best estimate of 555 + 354? (a) 1000 (b) 800 (c) 1200
  11. 11.Best estimate of 624 + 263? (a) 1100 (b) 700 (c) 900
  12. 12.Best estimate of 351 + 242? (a) 400 (b) 600 (c) 800
  13. 13.Best estimate of 359 + 649? (a) 1200 (b) 800 (c) 1000
  14. 14.Best estimate of 91 × 93? (a) 81000 (b) 8100 (c) 810
  15. 15.Best estimate of 629 + 576? (a) 1000 (b) 1200 (c) 1400
  16. 16.Best estimate of 72 × 70? (a) 490 (b) 49000 (c) 4900
  17. 17.Best estimate of 87 × 36? (a) 36000 (b) 360 (c) 3600
  18. 18.Best estimate of 21 × 53? (a) 100 (b) 10000 (c) 1000
  19. 19.Best estimate of 712 + 214? (a) 700 (b) 900 (c) 1100
  20. 20.Best estimate of 26 × 47? (a) 15000 (b) 1500 (c) 150
  21. 21.Best estimate of 92 × 31? (a) 2700 (b) 27000 (c) 270
  22. 22.Best estimate of 36 × 27? (a) 12000 (b) 1200 (c) 120
  23. 23.Best estimate of 579 + 427? (a) 1000 (b) 1200 (c) 800
  24. 24.Best estimate of 145 + 442? (a) 700 (b) 500 (c) 300
  25. 25.Best estimate of 24 × 63? (a) 120 (b) 12000 (c) 1200
  26. 26.Best estimate of 505 + 276? (a) 800 (b) 1000 (c) 600
  27. 27.Best estimate of 28 × 83? (a) 2400 (b) 240 (c) 24000
  28. 28.Best estimate of 42 × 40? (a) 1600 (b) 160 (c) 16000
  29. 29.Best estimate of 78 × 34? (a) 24000 (b) 2400 (c) 240
  30. 30.Best estimate of 780 + 159? (a) 1000 (b) 800 (c) 1200
  31. 31.Best estimate of 42 × 16? (a) 80 (b) 8000 (c) 800
  32. 32.Best estimate of 58 × 38? (a) 24000 (b) 240 (c) 2400
  33. 33.Best estimate of 13 × 61? (a) 60 (b) 6000 (c) 600
  34. 34.Best estimate of 52 × 53? (a) 250 (b) 2500 (c) 25000
  35. 35.Best estimate of 74 × 86? (a) 6300 (b) 63000 (c) 630
  36. 36.Best estimate of 70 × 98? (a) 7000 (b) 700 (c) 70000
  37. 37.Best estimate of 72 × 96? (a) 7000 (b) 700 (c) 70000
  38. 38.Best estimate of 195 + 195? (a) 600 (b) 400 (c) 200
  39. 39.Best estimate of 876 + 723? (a) 1800 (b) 1400 (c) 1600
  40. 40.Best estimate of 808 + 788? (a) 1800 (b) 1400 (c) 1600

Answer key

  1. 2700
  2. 3500
  3. 2100
  4. 900
  5. 800
  6. 1600
  7. 2700
  8. 2400
  9. 600
  10. 1000
  11. 900
  12. 600
  13. 1000
  14. 8100
  15. 1200
  16. 4900
  17. 3600
  18. 1000
  19. 900
  20. 1500
  21. 2700
  22. 1200
  23. 1000
  24. 500
  25. 1200
  26. 800
  27. 2400
  28. 1600
  29. 2400
  30. 1000
  31. 800
  32. 2400
  33. 600
  34. 2500
  35. 6300
  36. 7000
  37. 7000
  38. 400
  39. 1600
  40. 1600

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