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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 710 · 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 86 × 90? (a) 810 (b) 8100 (c) 81000
  2. 2.Best estimate of 18 × 14? (a) 20 (b) 200 (c) 2000
  3. 3.Best estimate of 354 + 245? (a) 400 (b) 600 (c) 800
  4. 4.Best estimate of 273 + 533? (a) 800 (b) 1000 (c) 600
  5. 5.Best estimate of 239 + 556? (a) 1000 (b) 600 (c) 800
  6. 6.Best estimate of 170 + 238? (a) 600 (b) 200 (c) 400
  7. 7.Best estimate of 535 + 354? (a) 900 (b) 1100 (c) 700
  8. 8.Best estimate of 798 + 810? (a) 1600 (b) 1800 (c) 1400
  9. 9.Best estimate of 68 × 71? (a) 4900 (b) 49000 (c) 490
  10. 10.Best estimate of 497 + 155? (a) 700 (b) 900 (c) 500
  11. 11.Best estimate of 873 + 720? (a) 1600 (b) 1800 (c) 1400
  12. 12.Best estimate of 96 × 41? (a) 40000 (b) 4000 (c) 400
  13. 13.Best estimate of 280 + 368? (a) 500 (b) 900 (c) 700
  14. 14.Best estimate of 16 × 26? (a) 600 (b) 60 (c) 6000
  15. 15.Best estimate of 98 × 31? (a) 30000 (b) 3000 (c) 300
  16. 16.Best estimate of 57 × 82? (a) 48000 (b) 4800 (c) 480
  17. 17.Best estimate of 78 × 13? (a) 80 (b) 800 (c) 8000
  18. 18.Best estimate of 690 + 734? (a) 1200 (b) 1400 (c) 1600
  19. 19.Best estimate of 351 + 389? (a) 1000 (b) 600 (c) 800
  20. 20.Best estimate of 62 × 80? (a) 48000 (b) 480 (c) 4800
  21. 21.Best estimate of 96 × 89? (a) 9000 (b) 90000 (c) 900
  22. 22.Best estimate of 572 + 536? (a) 1300 (b) 1100 (c) 900
  23. 23.Best estimate of 574 + 356? (a) 1000 (b) 800 (c) 1200
  24. 24.Best estimate of 26 × 38? (a) 120 (b) 1200 (c) 12000
  25. 25.Best estimate of 17 × 86? (a) 180 (b) 1800 (c) 18000
  26. 26.Best estimate of 81 × 76? (a) 6400 (b) 64000 (c) 640
  27. 27.Best estimate of 281 + 433? (a) 500 (b) 700 (c) 900
  28. 28.Best estimate of 79 × 90? (a) 72000 (b) 7200 (c) 720
  29. 29.Best estimate of 86 × 24? (a) 18000 (b) 1800 (c) 180
  30. 30.Best estimate of 63 × 39? (a) 2400 (b) 24000 (c) 240
  31. 31.Best estimate of 32 × 61? (a) 180 (b) 18000 (c) 1800
  32. 32.Best estimate of 458 + 826? (a) 1300 (b) 1100 (c) 1500
  33. 33.Best estimate of 88 × 33? (a) 270 (b) 27000 (c) 2700
  34. 34.Best estimate of 501 + 396? (a) 900 (b) 700 (c) 1100
  35. 35.Best estimate of 50 × 59? (a) 30000 (b) 3000 (c) 300
  36. 36.Best estimate of 52 × 86? (a) 45000 (b) 4500 (c) 450
  37. 37.Best estimate of 563 + 666? (a) 1300 (b) 1500 (c) 1100
  38. 38.Best estimate of 66 × 46? (a) 350 (b) 3500 (c) 35000
  39. 39.Best estimate of 432 + 403? (a) 800 (b) 1000 (c) 600
  40. 40.Best estimate of 738 + 806? (a) 1500 (b) 1700 (c) 1300

Answer key

  1. 8100
  2. 200
  3. 600
  4. 800
  5. 800
  6. 400
  7. 900
  8. 1600
  9. 4900
  10. 700
  11. 1600
  12. 4000
  13. 700
  14. 600
  15. 3000
  16. 4800
  17. 800
  18. 1400
  19. 800
  20. 4800
  21. 9000
  22. 1100
  23. 1000
  24. 1200
  25. 1800
  26. 6400
  27. 700
  28. 7200
  29. 1800
  30. 2400
  31. 1800
  32. 1300
  33. 2700
  34. 900
  35. 3000
  36. 4500
  37. 1300
  38. 3500
  39. 800
  40. 1500

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