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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 345 · 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 470 + 206? (a) 700 (b) 500 (c) 900
  2. 2.Best estimate of 79 × 61? (a) 48000 (b) 480 (c) 4800
  3. 3.Best estimate of 12 × 19? (a) 200 (b) 2000 (c) 20
  4. 4.Best estimate of 489 + 835? (a) 1300 (b) 1500 (c) 1100
  5. 5.Best estimate of 221 + 487? (a) 700 (b) 500 (c) 900
  6. 6.Best estimate of 173 + 534? (a) 900 (b) 700 (c) 500
  7. 7.Best estimate of 91 × 73? (a) 63000 (b) 6300 (c) 630
  8. 8.Best estimate of 19 × 17? (a) 400 (b) 40 (c) 4000
  9. 9.Best estimate of 19 × 70? (a) 1400 (b) 140 (c) 14000
  10. 10.Best estimate of 39 × 83? (a) 320 (b) 32000 (c) 3200
  11. 11.Best estimate of 172 + 184? (a) 600 (b) 200 (c) 400
  12. 12.Best estimate of 89 × 31? (a) 270 (b) 2700 (c) 27000
  13. 13.Best estimate of 36 × 53? (a) 2000 (b) 20000 (c) 200
  14. 14.Best estimate of 178 + 805? (a) 1000 (b) 1200 (c) 800
  15. 15.Best estimate of 27 × 97? (a) 300 (b) 30000 (c) 3000
  16. 16.Best estimate of 191 + 536? (a) 500 (b) 900 (c) 700
  17. 17.Best estimate of 29 × 67? (a) 21000 (b) 2100 (c) 210
  18. 18.Best estimate of 61 × 43? (a) 24000 (b) 2400 (c) 240
  19. 19.Best estimate of 18 × 67? (a) 1400 (b) 14000 (c) 140
  20. 20.Best estimate of 63 × 59? (a) 3600 (b) 36000 (c) 360
  21. 21.Best estimate of 81 × 46? (a) 4000 (b) 40000 (c) 400
  22. 22.Best estimate of 385 + 709? (a) 1100 (b) 1300 (c) 900
  23. 23.Best estimate of 54 × 17? (a) 10000 (b) 100 (c) 1000
  24. 24.Best estimate of 253 + 410? (a) 700 (b) 500 (c) 900
  25. 25.Best estimate of 204 + 723? (a) 700 (b) 1100 (c) 900
  26. 26.Best estimate of 19 × 73? (a) 1400 (b) 140 (c) 14000
  27. 27.Best estimate of 79 × 88? (a) 72000 (b) 7200 (c) 720
  28. 28.Best estimate of 346 + 459? (a) 800 (b) 1000 (c) 600
  29. 29.Best estimate of 62 × 33? (a) 18000 (b) 180 (c) 1800
  30. 30.Best estimate of 36 × 54? (a) 2000 (b) 200 (c) 20000
  31. 31.Best estimate of 58 × 62? (a) 360 (b) 3600 (c) 36000
  32. 32.Best estimate of 458 + 234? (a) 500 (b) 700 (c) 900
  33. 33.Best estimate of 81 × 43? (a) 3200 (b) 32000 (c) 320
  34. 34.Best estimate of 649 + 509? (a) 1100 (b) 900 (c) 1300
  35. 35.Best estimate of 694 + 640? (a) 1500 (b) 1100 (c) 1300
  36. 36.Best estimate of 725 + 629? (a) 1500 (b) 1100 (c) 1300
  37. 37.Best estimate of 322 + 485? (a) 800 (b) 600 (c) 1000
  38. 38.Best estimate of 70 × 98? (a) 700 (b) 70000 (c) 7000
  39. 39.Best estimate of 57 × 42? (a) 2400 (b) 240 (c) 24000
  40. 40.Best estimate of 77 × 36? (a) 3200 (b) 32000 (c) 320

Answer key

  1. 700
  2. 4800
  3. 200
  4. 1300
  5. 700
  6. 700
  7. 6300
  8. 400
  9. 1400
  10. 3200
  11. 400
  12. 2700
  13. 2000
  14. 1000
  15. 3000
  16. 700
  17. 2100
  18. 2400
  19. 1400
  20. 3600
  21. 4000
  22. 1100
  23. 1000
  24. 700
  25. 900
  26. 1400
  27. 7200
  28. 800
  29. 1800
  30. 2000
  31. 3600
  32. 700
  33. 3200
  34. 1100
  35. 1300
  36. 1300
  37. 800
  38. 7000
  39. 2400
  40. 3200

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