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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 2 · 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 19 × 19? (a) 40 (b) 400 (c) 4000
  2. 2.Best estimate of 676 + 565? (a) 1500 (b) 1300 (c) 1100
  3. 3.Best estimate of 333 + 221? (a) 300 (b) 700 (c) 500
  4. 4.Best estimate of 16 × 28? (a) 6000 (b) 600 (c) 60
  5. 5.Best estimate of 171 + 740? (a) 1100 (b) 700 (c) 900
  6. 6.Best estimate of 76 × 86? (a) 72000 (b) 720 (c) 7200
  7. 7.Best estimate of 461 + 630? (a) 1100 (b) 1300 (c) 900
  8. 8.Best estimate of 17 × 59? (a) 1200 (b) 120 (c) 12000
  9. 9.Best estimate of 66 × 23? (a) 14000 (b) 140 (c) 1400
  10. 10.Best estimate of 539 + 355? (a) 700 (b) 1100 (c) 900
  11. 11.Best estimate of 877 + 768? (a) 1700 (b) 1500 (c) 1900
  12. 12.Best estimate of 142 + 338? (a) 600 (b) 200 (c) 400
  13. 13.Best estimate of 94 × 47? (a) 4500 (b) 45000 (c) 450
  14. 14.Best estimate of 375 + 854? (a) 1300 (b) 1500 (c) 1100
  15. 15.Best estimate of 18 × 78? (a) 160 (b) 16000 (c) 1600
  16. 16.Best estimate of 16 × 61? (a) 12000 (b) 120 (c) 1200
  17. 17.Best estimate of 21 × 93? (a) 1800 (b) 18000 (c) 180
  18. 18.Best estimate of 303 + 148? (a) 400 (b) 600 (c) 200
  19. 19.Best estimate of 81 × 16? (a) 1600 (b) 16000 (c) 160
  20. 20.Best estimate of 56 × 50? (a) 300 (b) 3000 (c) 30000
  21. 21.Best estimate of 44 × 12? (a) 400 (b) 40 (c) 4000
  22. 22.Best estimate of 63 × 50? (a) 30000 (b) 300 (c) 3000
  23. 23.Best estimate of 34 × 88? (a) 27000 (b) 270 (c) 2700
  24. 24.Best estimate of 422 + 631? (a) 1200 (b) 800 (c) 1000
  25. 25.Best estimate of 343 + 268? (a) 600 (b) 800 (c) 400
  26. 26.Best estimate of 254 + 192? (a) 300 (b) 500 (c) 700
  27. 27.Best estimate of 204 + 398? (a) 600 (b) 400 (c) 800
  28. 28.Best estimate of 70 × 14? (a) 700 (b) 7000 (c) 70
  29. 29.Best estimate of 820 + 402? (a) 1200 (b) 1400 (c) 1000
  30. 30.Best estimate of 324 + 787? (a) 1100 (b) 1300 (c) 900
  31. 31.Best estimate of 60 × 29? (a) 180 (b) 18000 (c) 1800
  32. 32.Best estimate of 36 × 58? (a) 2400 (b) 24000 (c) 240
  33. 33.Best estimate of 63 × 54? (a) 30000 (b) 300 (c) 3000
  34. 34.Best estimate of 67 × 78? (a) 560 (b) 5600 (c) 56000
  35. 35.Best estimate of 461 + 666? (a) 1000 (b) 1400 (c) 1200
  36. 36.Best estimate of 160 + 458? (a) 900 (b) 700 (c) 500
  37. 37.Best estimate of 392 + 340? (a) 900 (b) 700 (c) 500
  38. 38.Best estimate of 465 + 459? (a) 800 (b) 1200 (c) 1000
  39. 39.Best estimate of 21 × 74? (a) 14000 (b) 1400 (c) 140
  40. 40.Best estimate of 59 × 21? (a) 12000 (b) 1200 (c) 120

Answer key

  1. 400
  2. 1300
  3. 500
  4. 600
  5. 900
  6. 7200
  7. 1100
  8. 1200
  9. 1400
  10. 900
  11. 1700
  12. 400
  13. 4500
  14. 1300
  15. 1600
  16. 1200
  17. 1800
  18. 400
  19. 1600
  20. 3000
  21. 400
  22. 3000
  23. 2700
  24. 1000
  25. 600
  26. 500
  27. 600
  28. 700
  29. 1200
  30. 1100
  31. 1800
  32. 2400
  33. 3000
  34. 5600
  35. 1200
  36. 700
  37. 700
  38. 1000
  39. 1400
  40. 1200

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