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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 200 · 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 60 × 70? (a) 4200 (b) 420 (c) 42000
  2. 2.Best estimate of 82 × 40? (a) 32000 (b) 3200 (c) 320
  3. 3.Best estimate of 78 × 86? (a) 720 (b) 7200 (c) 72000
  4. 4.Best estimate of 27 × 73? (a) 21000 (b) 210 (c) 2100
  5. 5.Best estimate of 393 + 309? (a) 500 (b) 900 (c) 700
  6. 6.Best estimate of 184 + 667? (a) 700 (b) 1100 (c) 900
  7. 7.Best estimate of 528 + 442? (a) 900 (b) 700 (c) 1100
  8. 8.Best estimate of 52 × 81? (a) 40000 (b) 400 (c) 4000
  9. 9.Best estimate of 304 + 492? (a) 600 (b) 1000 (c) 800
  10. 10.Best estimate of 634 + 431? (a) 1000 (b) 1200 (c) 800
  11. 11.Best estimate of 29 × 84? (a) 240 (b) 24000 (c) 2400
  12. 12.Best estimate of 312 + 848? (a) 1100 (b) 900 (c) 1300
  13. 13.Best estimate of 821 + 253? (a) 1100 (b) 900 (c) 1300
  14. 14.Best estimate of 245 + 591? (a) 800 (b) 1000 (c) 600
  15. 15.Best estimate of 81 × 36? (a) 3200 (b) 320 (c) 32000
  16. 16.Best estimate of 88 × 54? (a) 4500 (b) 45000 (c) 450
  17. 17.Best estimate of 86 × 97? (a) 90000 (b) 900 (c) 9000
  18. 18.Best estimate of 252 + 592? (a) 900 (b) 700 (c) 1100
  19. 19.Best estimate of 296 + 335? (a) 600 (b) 800 (c) 400
  20. 20.Best estimate of 27 × 59? (a) 180 (b) 1800 (c) 18000
  21. 21.Best estimate of 290 + 367? (a) 700 (b) 500 (c) 900
  22. 22.Best estimate of 20 × 61? (a) 12000 (b) 1200 (c) 120
  23. 23.Best estimate of 284 + 360? (a) 700 (b) 900 (c) 500
  24. 24.Best estimate of 66 × 20? (a) 140 (b) 14000 (c) 1400
  25. 25.Best estimate of 704 + 726? (a) 1600 (b) 1400 (c) 1200
  26. 26.Best estimate of 385 + 135? (a) 500 (b) 700 (c) 300
  27. 27.Best estimate of 182 + 607? (a) 800 (b) 1000 (c) 600
  28. 28.Best estimate of 228 + 355? (a) 600 (b) 800 (c) 400
  29. 29.Best estimate of 16 × 36? (a) 80 (b) 800 (c) 8000
  30. 30.Best estimate of 62 × 18? (a) 12000 (b) 120 (c) 1200
  31. 31.Best estimate of 835 + 824? (a) 1800 (b) 1600 (c) 1400
  32. 32.Best estimate of 195 + 362? (a) 800 (b) 400 (c) 600
  33. 33.Best estimate of 777 + 121? (a) 900 (b) 700 (c) 1100
  34. 34.Best estimate of 38 × 66? (a) 2800 (b) 280 (c) 28000
  35. 35.Best estimate of 26 × 19? (a) 600 (b) 6000 (c) 60
  36. 36.Best estimate of 28 × 63? (a) 1800 (b) 180 (c) 18000
  37. 37.Best estimate of 92 × 50? (a) 450 (b) 4500 (c) 45000
  38. 38.Best estimate of 240 + 602? (a) 600 (b) 800 (c) 1000
  39. 39.Best estimate of 185 + 329? (a) 300 (b) 700 (c) 500
  40. 40.Best estimate of 789 + 351? (a) 1400 (b) 1000 (c) 1200

Answer key

  1. 4200
  2. 3200
  3. 7200
  4. 2100
  5. 700
  6. 900
  7. 900
  8. 4000
  9. 800
  10. 1000
  11. 2400
  12. 1100
  13. 1100
  14. 800
  15. 3200
  16. 4500
  17. 9000
  18. 900
  19. 600
  20. 1800
  21. 700
  22. 1200
  23. 700
  24. 1400
  25. 1400
  26. 500
  27. 800
  28. 600
  29. 800
  30. 1200
  31. 1600
  32. 600
  33. 900
  34. 2800
  35. 600
  36. 1800
  37. 4500
  38. 800
  39. 500
  40. 1200

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