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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 830 · 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 380 + 451? (a) 700 (b) 1100 (c) 900
  2. 2.Best estimate of 288 + 295? (a) 800 (b) 600 (c) 400
  3. 3.Best estimate of 37 × 54? (a) 200 (b) 2000 (c) 20000
  4. 4.Best estimate of 819 + 333? (a) 1100 (b) 900 (c) 1300
  5. 5.Best estimate of 96 × 37? (a) 400 (b) 40000 (c) 4000
  6. 6.Best estimate of 21 × 36? (a) 800 (b) 8000 (c) 80
  7. 7.Best estimate of 293 + 317? (a) 400 (b) 800 (c) 600
  8. 8.Best estimate of 251 + 625? (a) 900 (b) 700 (c) 1100
  9. 9.Best estimate of 79 × 34? (a) 24000 (b) 240 (c) 2400
  10. 10.Best estimate of 44 × 80? (a) 3200 (b) 320 (c) 32000
  11. 11.Best estimate of 83 × 19? (a) 16000 (b) 1600 (c) 160
  12. 12.Best estimate of 69 × 87? (a) 630 (b) 63000 (c) 6300
  13. 13.Best estimate of 83 × 26? (a) 2400 (b) 24000 (c) 240
  14. 14.Best estimate of 29 × 77? (a) 24000 (b) 240 (c) 2400
  15. 15.Best estimate of 49 × 26? (a) 1500 (b) 150 (c) 15000
  16. 16.Best estimate of 69 × 58? (a) 42000 (b) 4200 (c) 420
  17. 17.Best estimate of 420 + 630? (a) 1200 (b) 1000 (c) 800
  18. 18.Best estimate of 364 + 694? (a) 1300 (b) 900 (c) 1100
  19. 19.Best estimate of 198 + 696? (a) 700 (b) 900 (c) 1100
  20. 20.Best estimate of 277 + 218? (a) 500 (b) 700 (c) 300
  21. 21.Best estimate of 49 × 32? (a) 1500 (b) 15000 (c) 150
  22. 22.Best estimate of 90 × 56? (a) 540 (b) 5400 (c) 54000
  23. 23.Best estimate of 20 × 12? (a) 2000 (b) 20 (c) 200
  24. 24.Best estimate of 40 × 36? (a) 16000 (b) 160 (c) 1600
  25. 25.Best estimate of 676 + 665? (a) 1400 (b) 1200 (c) 1600
  26. 26.Best estimate of 468 + 786? (a) 1500 (b) 1100 (c) 1300
  27. 27.Best estimate of 374 + 293? (a) 700 (b) 500 (c) 900
  28. 28.Best estimate of 82 × 72? (a) 56000 (b) 5600 (c) 560
  29. 29.Best estimate of 593 + 306? (a) 1100 (b) 900 (c) 700
  30. 30.Best estimate of 86 × 66? (a) 630 (b) 63000 (c) 6300
  31. 31.Best estimate of 128 + 296? (a) 400 (b) 600 (c) 200
  32. 32.Best estimate of 310 + 290? (a) 800 (b) 400 (c) 600
  33. 33.Best estimate of 865 + 477? (a) 1400 (b) 1600 (c) 1200
  34. 34.Best estimate of 41 × 79? (a) 32000 (b) 320 (c) 3200
  35. 35.Best estimate of 22 × 86? (a) 1800 (b) 18000 (c) 180
  36. 36.Best estimate of 67 × 36? (a) 2800 (b) 28000 (c) 280
  37. 37.Best estimate of 34 × 36? (a) 12000 (b) 1200 (c) 120
  38. 38.Best estimate of 16 × 12? (a) 200 (b) 2000 (c) 20
  39. 39.Best estimate of 69 × 90? (a) 63000 (b) 630 (c) 6300
  40. 40.Best estimate of 68 × 34? (a) 210 (b) 21000 (c) 2100

Answer key

  1. 900
  2. 600
  3. 2000
  4. 1100
  5. 4000
  6. 800
  7. 600
  8. 900
  9. 2400
  10. 3200
  11. 1600
  12. 6300
  13. 2400
  14. 2400
  15. 1500
  16. 4200
  17. 1000
  18. 1100
  19. 900
  20. 500
  21. 1500
  22. 5400
  23. 200
  24. 1600
  25. 1400
  26. 1300
  27. 700
  28. 5600
  29. 900
  30. 6300
  31. 400
  32. 600
  33. 1400
  34. 3200
  35. 1800
  36. 2800
  37. 1200
  38. 200
  39. 6300
  40. 2100

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