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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 940 · 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 74 × 62? (a) 420 (b) 42000 (c) 4200
  2. 2.Best estimate of 97 × 14? (a) 100 (b) 1000 (c) 10000
  3. 3.Best estimate of 746 + 613? (a) 1500 (b) 1300 (c) 1100
  4. 4.Best estimate of 42 × 44? (a) 1600 (b) 16000 (c) 160
  5. 5.Best estimate of 874 + 264? (a) 1000 (b) 1200 (c) 1400
  6. 6.Best estimate of 391 + 355? (a) 800 (b) 1000 (c) 600
  7. 7.Best estimate of 18 × 20? (a) 400 (b) 4000 (c) 40
  8. 8.Best estimate of 36 × 53? (a) 20000 (b) 200 (c) 2000
  9. 9.Best estimate of 180 + 505? (a) 700 (b) 500 (c) 900
  10. 10.Best estimate of 81 × 39? (a) 3200 (b) 320 (c) 32000
  11. 11.Best estimate of 365 + 356? (a) 600 (b) 1000 (c) 800
  12. 12.Best estimate of 870 + 812? (a) 1700 (b) 1900 (c) 1500
  13. 13.Best estimate of 345 + 157? (a) 700 (b) 300 (c) 500
  14. 14.Best estimate of 54 × 33? (a) 15000 (b) 150 (c) 1500
  15. 15.Best estimate of 517 + 441? (a) 700 (b) 900 (c) 1100
  16. 16.Best estimate of 157 + 328? (a) 700 (b) 300 (c) 500
  17. 17.Best estimate of 230 + 172? (a) 200 (b) 400 (c) 600
  18. 18.Best estimate of 314 + 319? (a) 800 (b) 400 (c) 600
  19. 19.Best estimate of 665 + 624? (a) 1500 (b) 1100 (c) 1300
  20. 20.Best estimate of 335 + 517? (a) 800 (b) 600 (c) 1000
  21. 21.Best estimate of 418 + 307? (a) 500 (b) 700 (c) 900
  22. 22.Best estimate of 88 × 79? (a) 720 (b) 7200 (c) 72000
  23. 23.Best estimate of 86 × 90? (a) 8100 (b) 81000 (c) 810
  24. 24.Best estimate of 12 × 49? (a) 500 (b) 5000 (c) 50
  25. 25.Best estimate of 63 × 39? (a) 24000 (b) 240 (c) 2400
  26. 26.Best estimate of 19 × 84? (a) 16000 (b) 1600 (c) 160
  27. 27.Best estimate of 280 + 139? (a) 400 (b) 200 (c) 600
  28. 28.Best estimate of 156 + 560? (a) 800 (b) 600 (c) 1000
  29. 29.Best estimate of 427 + 429? (a) 800 (b) 600 (c) 1000
  30. 30.Best estimate of 79 × 26? (a) 2400 (b) 24000 (c) 240
  31. 31.Best estimate of 12 × 60? (a) 6000 (b) 60 (c) 600
  32. 32.Best estimate of 60 × 33? (a) 18000 (b) 180 (c) 1800
  33. 33.Best estimate of 755 + 414? (a) 1200 (b) 1400 (c) 1000
  34. 34.Best estimate of 13 × 66? (a) 70 (b) 7000 (c) 700
  35. 35.Best estimate of 718 + 434? (a) 900 (b) 1300 (c) 1100
  36. 36.Best estimate of 96 × 97? (a) 1000 (b) 10000 (c) 100000
  37. 37.Best estimate of 356 + 265? (a) 500 (b) 700 (c) 900
  38. 38.Best estimate of 90 × 98? (a) 900 (b) 9000 (c) 90000
  39. 39.Best estimate of 64 × 94? (a) 54000 (b) 5400 (c) 540
  40. 40.Best estimate of 16 × 32? (a) 60 (b) 600 (c) 6000

Answer key

  1. 4200
  2. 1000
  3. 1300
  4. 1600
  5. 1200
  6. 800
  7. 400
  8. 2000
  9. 700
  10. 3200
  11. 800
  12. 1700
  13. 500
  14. 1500
  15. 900
  16. 500
  17. 400
  18. 600
  19. 1300
  20. 800
  21. 700
  22. 7200
  23. 8100
  24. 500
  25. 2400
  26. 1600
  27. 400
  28. 800
  29. 800
  30. 2400
  31. 600
  32. 1800
  33. 1200
  34. 700
  35. 1100
  36. 10000
  37. 700
  38. 9000
  39. 5400
  40. 600

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