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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 411 · 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 93 × 61? (a) 5400 (b) 540 (c) 54000
  2. 2.Best estimate of 93 × 14? (a) 900 (b) 90 (c) 9000
  3. 3.Best estimate of 40 × 38? (a) 1600 (b) 16000 (c) 160
  4. 4.Best estimate of 572 + 184? (a) 600 (b) 800 (c) 1000
  5. 5.Best estimate of 359 + 402? (a) 800 (b) 600 (c) 1000
  6. 6.Best estimate of 86 × 96? (a) 900 (b) 9000 (c) 90000
  7. 7.Best estimate of 473 + 536? (a) 1000 (b) 800 (c) 1200
  8. 8.Best estimate of 703 + 720? (a) 1600 (b) 1400 (c) 1200
  9. 9.Best estimate of 723 + 205? (a) 1100 (b) 700 (c) 900
  10. 10.Best estimate of 321 + 404? (a) 700 (b) 500 (c) 900
  11. 11.Best estimate of 80 × 47? (a) 40000 (b) 400 (c) 4000
  12. 12.Best estimate of 16 × 18? (a) 400 (b) 40 (c) 4000
  13. 13.Best estimate of 72 × 16? (a) 14000 (b) 1400 (c) 140
  14. 14.Best estimate of 28 × 32? (a) 900 (b) 9000 (c) 90
  15. 15.Best estimate of 309 + 313? (a) 600 (b) 800 (c) 400
  16. 16.Best estimate of 819 + 329? (a) 900 (b) 1300 (c) 1100
  17. 17.Best estimate of 17 × 83? (a) 16000 (b) 1600 (c) 160
  18. 18.Best estimate of 17 × 16? (a) 4000 (b) 40 (c) 400
  19. 19.Best estimate of 56 × 73? (a) 42000 (b) 4200 (c) 420
  20. 20.Best estimate of 511 + 417? (a) 700 (b) 1100 (c) 900
  21. 21.Best estimate of 37 × 22? (a) 8000 (b) 800 (c) 80
  22. 22.Best estimate of 41 × 50? (a) 20000 (b) 200 (c) 2000
  23. 23.Best estimate of 160 + 351? (a) 400 (b) 600 (c) 800
  24. 24.Best estimate of 70 × 42? (a) 2800 (b) 28000 (c) 280
  25. 25.Best estimate of 494 + 403? (a) 900 (b) 700 (c) 1100
  26. 26.Best estimate of 49 × 86? (a) 450 (b) 4500 (c) 45000
  27. 27.Best estimate of 377 + 488? (a) 900 (b) 1100 (c) 700
  28. 28.Best estimate of 378 + 638? (a) 1200 (b) 800 (c) 1000
  29. 29.Best estimate of 76 × 32? (a) 24000 (b) 2400 (c) 240
  30. 30.Best estimate of 370 + 371? (a) 1000 (b) 600 (c) 800
  31. 31.Best estimate of 13 × 27? (a) 3000 (b) 30 (c) 300
  32. 32.Best estimate of 70 × 54? (a) 35000 (b) 3500 (c) 350
  33. 33.Best estimate of 20 × 37? (a) 80 (b) 800 (c) 8000
  34. 34.Best estimate of 34 × 16? (a) 6000 (b) 600 (c) 60
  35. 35.Best estimate of 836 + 699? (a) 1500 (b) 1700 (c) 1300
  36. 36.Best estimate of 87 × 74? (a) 6300 (b) 630 (c) 63000
  37. 37.Best estimate of 68 × 39? (a) 2800 (b) 280 (c) 28000
  38. 38.Best estimate of 144 + 364? (a) 500 (b) 300 (c) 700
  39. 39.Best estimate of 178 + 553? (a) 1000 (b) 600 (c) 800
  40. 40.Best estimate of 843 + 719? (a) 1700 (b) 1300 (c) 1500

Answer key

  1. 5400
  2. 900
  3. 1600
  4. 800
  5. 800
  6. 9000
  7. 1000
  8. 1400
  9. 900
  10. 700
  11. 4000
  12. 400
  13. 1400
  14. 900
  15. 600
  16. 1100
  17. 1600
  18. 400
  19. 4200
  20. 900
  21. 800
  22. 2000
  23. 600
  24. 2800
  25. 900
  26. 4500
  27. 900
  28. 1000
  29. 2400
  30. 800
  31. 300
  32. 3500
  33. 800
  34. 600
  35. 1500
  36. 6300
  37. 2800
  38. 500
  39. 800
  40. 1500

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