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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 135 · 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 144 + 461? (a) 400 (b) 600 (c) 800
  2. 2.Best estimate of 79 × 84? (a) 640 (b) 6400 (c) 64000
  3. 3.Best estimate of 73 × 16? (a) 1400 (b) 14000 (c) 140
  4. 4.Best estimate of 134 + 222? (a) 500 (b) 300 (c) 100
  5. 5.Best estimate of 36 × 42? (a) 160 (b) 1600 (c) 16000
  6. 6.Best estimate of 440 + 294? (a) 900 (b) 700 (c) 500
  7. 7.Best estimate of 473 + 477? (a) 1200 (b) 1000 (c) 800
  8. 8.Best estimate of 566 + 474? (a) 1300 (b) 900 (c) 1100
  9. 9.Best estimate of 138 + 140? (a) 400 (b) 200 (c) 0
  10. 10.Best estimate of 69 × 91? (a) 63000 (b) 6300 (c) 630
  11. 11.Best estimate of 632 + 399? (a) 1000 (b) 1200 (c) 800
  12. 12.Best estimate of 82 × 56? (a) 4800 (b) 480 (c) 48000
  13. 13.Best estimate of 555 + 476? (a) 1100 (b) 900 (c) 1300
  14. 14.Best estimate of 373 + 801? (a) 1000 (b) 1200 (c) 1400
  15. 15.Best estimate of 28 × 78? (a) 2400 (b) 24000 (c) 240
  16. 16.Best estimate of 14 × 16? (a) 20 (b) 2000 (c) 200
  17. 17.Best estimate of 26 × 36? (a) 1200 (b) 12000 (c) 120
  18. 18.Best estimate of 74 × 52? (a) 350 (b) 3500 (c) 35000
  19. 19.Best estimate of 63 × 84? (a) 4800 (b) 480 (c) 48000
  20. 20.Best estimate of 213 + 523? (a) 700 (b) 500 (c) 900
  21. 21.Best estimate of 669 + 270? (a) 1000 (b) 1200 (c) 800
  22. 22.Best estimate of 541 + 532? (a) 1000 (b) 1200 (c) 800
  23. 23.Best estimate of 88 × 39? (a) 360 (b) 3600 (c) 36000
  24. 24.Best estimate of 17 × 51? (a) 1000 (b) 100 (c) 10000
  25. 25.Best estimate of 38 × 18? (a) 80 (b) 800 (c) 8000
  26. 26.Best estimate of 213 + 175? (a) 400 (b) 200 (c) 600
  27. 27.Best estimate of 68 × 18? (a) 140 (b) 1400 (c) 14000
  28. 28.Best estimate of 856 + 382? (a) 1300 (b) 1500 (c) 1100
  29. 29.Best estimate of 314 + 658? (a) 1200 (b) 1000 (c) 800
  30. 30.Best estimate of 20 × 80? (a) 160 (b) 1600 (c) 16000
  31. 31.Best estimate of 245 + 683? (a) 900 (b) 1100 (c) 700
  32. 32.Best estimate of 30 × 86? (a) 27000 (b) 2700 (c) 270
  33. 33.Best estimate of 53 × 26? (a) 150 (b) 15000 (c) 1500
  34. 34.Best estimate of 89 × 90? (a) 8100 (b) 81000 (c) 810
  35. 35.Best estimate of 40 × 70? (a) 28000 (b) 280 (c) 2800
  36. 36.Best estimate of 19 × 91? (a) 18000 (b) 180 (c) 1800
  37. 37.Best estimate of 57 × 48? (a) 300 (b) 30000 (c) 3000
  38. 38.Best estimate of 796 + 642? (a) 1200 (b) 1400 (c) 1600
  39. 39.Best estimate of 814 + 782? (a) 1400 (b) 1600 (c) 1800
  40. 40.Best estimate of 29 × 84? (a) 2400 (b) 24000 (c) 240

Answer key

  1. 600
  2. 6400
  3. 1400
  4. 300
  5. 1600
  6. 700
  7. 1000
  8. 1100
  9. 200
  10. 6300
  11. 1000
  12. 4800
  13. 1100
  14. 1200
  15. 2400
  16. 200
  17. 1200
  18. 3500
  19. 4800
  20. 700
  21. 1000
  22. 1000
  23. 3600
  24. 1000
  25. 800
  26. 400
  27. 1400
  28. 1300
  29. 1000
  30. 1600
  31. 900
  32. 2700
  33. 1500
  34. 8100
  35. 2800
  36. 1800
  37. 3000
  38. 1400
  39. 1600
  40. 2400

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