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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 501 · 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. 1.987 − 799 =
  2. 2.649 − 607 =
  3. 3.948 − 199 =
  4. 4.745 − 699 =
  5. 5.511 − 399 =
  6. 6.473 − 197 =
  7. 7.476 − 298 =
  8. 8.897 − 199 =
  9. 9.863 − 798 =
  10. 10.747 − 497 =
  11. 11.561 − 497 =
  12. 12.763 − 297 =
  13. 13.618 − 598 =
  14. 14.260 − 199 =
  15. 15.727 − 699 =
  16. 16.751 − 699 =
  17. 17.716 − 517 =
  18. 18.396 − 339 =
  19. 19.794 − 398 =
  20. 20.625 − 598 =
  21. 21.341 − 299 =
  22. 22.321 − 298 =
  23. 23.476 − 397 =
  24. 24.563 − 399 =
  25. 25.933 − 197 =
  26. 26.615 − 577 =
  27. 27.689 − 409 =
  28. 28.986 − 208 =
  29. 29.960 − 297 =
  30. 30.837 − 198 =
  31. 31.534 − 169 =
  32. 32.982 − 488 =
  33. 33.396 − 299 =
  34. 34.440 − 299 =
  35. 35.656 − 628 =
  36. 36.439 − 398 =
  37. 37.852 − 398 =
  38. 38.804 − 599 =
  39. 39.904 − 297 =
  40. 40.788 − 299 =

Answer key

  1. 188
  2. 42
  3. 749
  4. 46
  5. 112
  6. 276
  7. 178
  8. 698
  9. 65
  10. 250
  11. 64
  12. 466
  13. 20
  14. 61
  15. 28
  16. 52
  17. 199
  18. 57
  19. 396
  20. 27
  21. 42
  22. 23
  23. 79
  24. 164
  25. 736
  26. 38
  27. 280
  28. 778
  29. 663
  30. 639
  31. 365
  32. 494
  33. 97
  34. 141
  35. 28
  36. 41
  37. 454
  38. 205
  39. 607
  40. 489

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