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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 933 · 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 433 + 442? (a) 800 (b) 1000 (c) 600
  2. 2.Best estimate of 421 + 203? (a) 600 (b) 400 (c) 800
  3. 3.Best estimate of 211 + 555? (a) 1000 (b) 600 (c) 800
  4. 4.Best estimate of 539 + 419? (a) 900 (b) 1100 (c) 700
  5. 5.Best estimate of 91 × 92? (a) 8100 (b) 81000 (c) 810
  6. 6.Best estimate of 238 + 149? (a) 500 (b) 300 (c) 100
  7. 7.Best estimate of 259 + 337? (a) 800 (b) 400 (c) 600
  8. 8.Best estimate of 38 × 26? (a) 12000 (b) 120 (c) 1200
  9. 9.Best estimate of 732 + 166? (a) 700 (b) 900 (c) 1100
  10. 10.Best estimate of 84 × 72? (a) 5600 (b) 56000 (c) 560
  11. 11.Best estimate of 544 + 152? (a) 500 (b) 900 (c) 700
  12. 12.Best estimate of 70 × 16? (a) 140 (b) 14000 (c) 1400
  13. 13.Best estimate of 16 × 91? (a) 1800 (b) 180 (c) 18000
  14. 14.Best estimate of 51 × 64? (a) 3000 (b) 30000 (c) 300
  15. 15.Best estimate of 572 + 413? (a) 1200 (b) 800 (c) 1000
  16. 16.Best estimate of 89 × 21? (a) 1800 (b) 18000 (c) 180
  17. 17.Best estimate of 193 + 811? (a) 1200 (b) 1000 (c) 800
  18. 18.Best estimate of 79 × 82? (a) 64000 (b) 640 (c) 6400
  19. 19.Best estimate of 26 × 16? (a) 6000 (b) 600 (c) 60
  20. 20.Best estimate of 88 × 47? (a) 450 (b) 45000 (c) 4500
  21. 21.Best estimate of 245 + 204? (a) 400 (b) 200 (c) 600
  22. 22.Best estimate of 34 × 27? (a) 900 (b) 90 (c) 9000
  23. 23.Best estimate of 56 × 56? (a) 3600 (b) 360 (c) 36000
  24. 24.Best estimate of 163 + 365? (a) 400 (b) 600 (c) 800
  25. 25.Best estimate of 703 + 838? (a) 1300 (b) 1700 (c) 1500
  26. 26.Best estimate of 53 × 18? (a) 10000 (b) 1000 (c) 100
  27. 27.Best estimate of 62 × 62? (a) 3600 (b) 360 (c) 36000
  28. 28.Best estimate of 28 × 90? (a) 2700 (b) 270 (c) 27000
  29. 29.Best estimate of 24 × 51? (a) 1000 (b) 10000 (c) 100
  30. 30.Best estimate of 766 + 302? (a) 900 (b) 1100 (c) 1300
  31. 31.Best estimate of 305 + 616? (a) 900 (b) 1100 (c) 700
  32. 32.Best estimate of 81 × 23? (a) 160 (b) 1600 (c) 16000
  33. 33.Best estimate of 207 + 326? (a) 500 (b) 700 (c) 300
  34. 34.Best estimate of 38 × 76? (a) 32000 (b) 320 (c) 3200
  35. 35.Best estimate of 76 × 20? (a) 1600 (b) 160 (c) 16000
  36. 36.Best estimate of 80 × 49? (a) 4000 (b) 40000 (c) 400
  37. 37.Best estimate of 742 + 197? (a) 700 (b) 900 (c) 1100
  38. 38.Best estimate of 700 + 647? (a) 1300 (b) 1500 (c) 1100
  39. 39.Best estimate of 30 × 90? (a) 2700 (b) 270 (c) 27000
  40. 40.Best estimate of 559 + 805? (a) 1400 (b) 1600 (c) 1200

Answer key

  1. 800
  2. 600
  3. 800
  4. 900
  5. 8100
  6. 300
  7. 600
  8. 1200
  9. 900
  10. 5600
  11. 700
  12. 1400
  13. 1800
  14. 3000
  15. 1000
  16. 1800
  17. 1000
  18. 6400
  19. 600
  20. 4500
  21. 400
  22. 900
  23. 3600
  24. 600
  25. 1500
  26. 1000
  27. 3600
  28. 2700
  29. 1000
  30. 1100
  31. 900
  32. 1600
  33. 500
  34. 3200
  35. 1600
  36. 4000
  37. 900
  38. 1300
  39. 2700
  40. 1400

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