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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 879 · 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 425 + 728? (a) 1100 (b) 1300 (c) 900
  2. 2.Best estimate of 30 × 87? (a) 270 (b) 2700 (c) 27000
  3. 3.Best estimate of 21 × 26? (a) 6000 (b) 600 (c) 60
  4. 4.Best estimate of 54 × 29? (a) 150 (b) 15000 (c) 1500
  5. 5.Best estimate of 20 × 73? (a) 14000 (b) 1400 (c) 140
  6. 6.Best estimate of 97 × 29? (a) 30000 (b) 3000 (c) 300
  7. 7.Best estimate of 318 + 569? (a) 700 (b) 900 (c) 1100
  8. 8.Best estimate of 624 + 685? (a) 1500 (b) 1100 (c) 1300
  9. 9.Best estimate of 416 + 182? (a) 400 (b) 600 (c) 800
  10. 10.Best estimate of 509 + 642? (a) 900 (b) 1100 (c) 1300
  11. 11.Best estimate of 56 × 32? (a) 1800 (b) 18000 (c) 180
  12. 12.Best estimate of 93 × 16? (a) 180 (b) 1800 (c) 18000
  13. 13.Best estimate of 63 × 91? (a) 54000 (b) 5400 (c) 540
  14. 14.Best estimate of 262 + 541? (a) 800 (b) 600 (c) 1000
  15. 15.Best estimate of 826 + 260? (a) 900 (b) 1300 (c) 1100
  16. 16.Best estimate of 17 × 17? (a) 400 (b) 40 (c) 4000
  17. 17.Best estimate of 17 × 91? (a) 18000 (b) 180 (c) 1800
  18. 18.Best estimate of 427 + 173? (a) 400 (b) 600 (c) 800
  19. 19.Best estimate of 779 + 710? (a) 1500 (b) 1700 (c) 1300
  20. 20.Best estimate of 343 + 428? (a) 500 (b) 700 (c) 900
  21. 21.Best estimate of 72 × 19? (a) 1400 (b) 14000 (c) 140
  22. 22.Best estimate of 13 × 89? (a) 90 (b) 900 (c) 9000
  23. 23.Best estimate of 78 × 59? (a) 48000 (b) 480 (c) 4800
  24. 24.Best estimate of 128 + 774? (a) 1100 (b) 700 (c) 900
  25. 25.Best estimate of 13 × 12? (a) 100 (b) 1000 (c) 10
  26. 26.Best estimate of 89 × 98? (a) 90000 (b) 9000 (c) 900
  27. 27.Best estimate of 509 + 729? (a) 1400 (b) 1200 (c) 1000
  28. 28.Best estimate of 68 × 96? (a) 70000 (b) 7000 (c) 700
  29. 29.Best estimate of 692 + 286? (a) 1200 (b) 800 (c) 1000
  30. 30.Best estimate of 24 × 86? (a) 1800 (b) 180 (c) 18000
  31. 31.Best estimate of 815 + 561? (a) 1600 (b) 1200 (c) 1400
  32. 32.Best estimate of 617 + 864? (a) 1500 (b) 1300 (c) 1700
  33. 33.Best estimate of 98 × 68? (a) 7000 (b) 700 (c) 70000
  34. 34.Best estimate of 20 × 78? (a) 1600 (b) 16000 (c) 160
  35. 35.Best estimate of 821 + 163? (a) 1000 (b) 1200 (c) 800
  36. 36.Best estimate of 42 × 13? (a) 4000 (b) 400 (c) 40
  37. 37.Best estimate of 77 × 88? (a) 72000 (b) 720 (c) 7200
  38. 38.Best estimate of 283 + 603? (a) 1100 (b) 900 (c) 700
  39. 39.Best estimate of 67 × 46? (a) 3500 (b) 35000 (c) 350
  40. 40.Best estimate of 490 + 665? (a) 1200 (b) 1000 (c) 1400

Answer key

  1. 1100
  2. 2700
  3. 600
  4. 1500
  5. 1400
  6. 3000
  7. 900
  8. 1300
  9. 600
  10. 1100
  11. 1800
  12. 1800
  13. 5400
  14. 800
  15. 1100
  16. 400
  17. 1800
  18. 600
  19. 1500
  20. 700
  21. 1400
  22. 900
  23. 4800
  24. 900
  25. 100
  26. 9000
  27. 1200
  28. 7000
  29. 1000
  30. 1800
  31. 1400
  32. 1500
  33. 7000
  34. 1600
  35. 1000
  36. 400
  37. 7200
  38. 900
  39. 3500
  40. 1200

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