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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 298 · 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. 1.377 − 147 =
  2. 2.656 − 299 =
  3. 3.828 − 797 =
  4. 4.550 − 138 =
  5. 5.945 − 639 =
  6. 6.989 − 697 =
  7. 7.858 − 199 =
  8. 8.593 − 199 =
  9. 9.432 − 348 =
  10. 10.950 − 237 =
  11. 11.427 − 407 =
  12. 12.867 − 499 =
  13. 13.975 − 799 =
  14. 14.605 − 477 =
  15. 15.168 − 138 =
  16. 16.901 − 797 =
  17. 17.775 − 618 =
  18. 18.937 − 797 =
  19. 19.537 − 397 =
  20. 20.663 − 499 =
  21. 21.266 − 188 =
  22. 22.341 − 197 =
  23. 23.956 − 197 =
  24. 24.746 − 688 =
  25. 25.297 − 277 =
  26. 26.753 − 598 =
  27. 27.579 − 497 =
  28. 28.763 − 518 =
  29. 29.292 − 148 =
  30. 30.643 − 197 =
  31. 31.207 − 118 =
  32. 32.736 − 197 =
  33. 33.711 − 499 =
  34. 34.574 − 298 =
  35. 35.615 − 598 =
  36. 36.482 − 199 =
  37. 37.864 − 397 =
  38. 38.909 − 297 =
  39. 39.911 − 569 =
  40. 40.776 − 569 =

Answer key

  1. 230
  2. 357
  3. 31
  4. 412
  5. 306
  6. 292
  7. 659
  8. 394
  9. 84
  10. 713
  11. 20
  12. 368
  13. 176
  14. 128
  15. 30
  16. 104
  17. 157
  18. 140
  19. 140
  20. 164
  21. 78
  22. 144
  23. 759
  24. 58
  25. 20
  26. 155
  27. 82
  28. 245
  29. 144
  30. 446
  31. 89
  32. 539
  33. 212
  34. 276
  35. 17
  36. 283
  37. 467
  38. 612
  39. 342
  40. 207

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