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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 636 · 40 questions
TalentJR

How to do it in your head (Round up, add back): Round the number you take away up to the next ten or hundred: 297 → 300 (3 too many). Take away the round number. Add back the extra, because you took away too much.

NameDateTime takenScore ___ / 40
  1. 1.720 − 197 =
  2. 2.591 − 157 =
  3. 3.798 − 599 =
  4. 4.490 − 399 =
  5. 5.537 − 398 =
  6. 6.782 − 699 =
  7. 7.807 − 678 =
  8. 8.930 − 199 =
  9. 9.652 − 579 =
  10. 10.655 − 399 =
  11. 11.731 − 628 =
  12. 12.567 − 499 =
  13. 13.502 − 199 =
  14. 14.917 − 798 =
  15. 15.512 − 299 =
  16. 16.525 − 398 =
  17. 17.942 − 699 =
  18. 18.664 − 417 =
  19. 19.260 − 169 =
  20. 20.977 − 797 =
  21. 21.565 − 399 =
  22. 22.626 − 597 =
  23. 23.679 − 378 =
  24. 24.898 − 299 =
  25. 25.364 − 149 =
  26. 26.834 − 797 =
  27. 27.465 − 398 =
  28. 28.862 − 548 =
  29. 29.623 − 398 =
  30. 30.984 − 798 =
  31. 31.691 − 399 =
  32. 32.632 − 499 =
  33. 33.848 − 159 =
  34. 34.651 − 459 =
  35. 35.612 − 298 =
  36. 36.339 − 299 =
  37. 37.885 − 399 =
  38. 38.356 − 197 =
  39. 39.910 − 599 =
  40. 40.881 − 397 =

Answer key

  1. 523
  2. 434
  3. 199
  4. 91
  5. 139
  6. 83
  7. 129
  8. 731
  9. 73
  10. 256
  11. 103
  12. 68
  13. 303
  14. 119
  15. 213
  16. 127
  17. 243
  18. 247
  19. 91
  20. 180
  21. 166
  22. 29
  23. 301
  24. 599
  25. 215
  26. 37
  27. 67
  28. 314
  29. 225
  30. 186
  31. 292
  32. 133
  33. 689
  34. 192
  35. 314
  36. 40
  37. 486
  38. 159
  39. 311
  40. 484

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