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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 776 · 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. 1.627 − 498 =
  2. 2.440 − 397 =
  3. 3.541 − 397 =
  4. 4.848 − 798 =
  5. 5.676 − 598 =
  6. 6.965 − 198 =
  7. 7.444 − 399 =
  8. 8.735 − 607 =
  9. 9.824 − 498 =
  10. 10.869 − 698 =
  11. 11.596 − 197 =
  12. 12.772 − 169 =
  13. 13.935 − 299 =
  14. 14.331 − 197 =
  15. 15.914 − 598 =
  16. 16.160 − 139 =
  17. 17.832 − 797 =
  18. 18.319 − 297 =
  19. 19.904 − 668 =
  20. 20.753 − 599 =
  21. 21.588 − 267 =
  22. 22.676 − 397 =
  23. 23.546 − 218 =
  24. 24.799 − 417 =
  25. 25.412 − 399 =
  26. 26.706 − 497 =
  27. 27.590 − 508 =
  28. 28.719 − 297 =
  29. 29.838 − 397 =
  30. 30.777 − 499 =
  31. 31.788 − 398 =
  32. 32.880 − 799 =
  33. 33.675 − 597 =
  34. 34.347 − 299 =
  35. 35.713 − 597 =
  36. 36.618 − 588 =
  37. 37.785 − 519 =
  38. 38.385 − 237 =
  39. 39.762 − 548 =
  40. 40.801 − 497 =

Answer key

  1. 129
  2. 43
  3. 144
  4. 50
  5. 78
  6. 767
  7. 45
  8. 128
  9. 326
  10. 171
  11. 399
  12. 603
  13. 636
  14. 134
  15. 316
  16. 21
  17. 35
  18. 22
  19. 236
  20. 154
  21. 321
  22. 279
  23. 328
  24. 382
  25. 13
  26. 209
  27. 82
  28. 422
  29. 441
  30. 278
  31. 390
  32. 81
  33. 78
  34. 48
  35. 116
  36. 30
  37. 266
  38. 148
  39. 214
  40. 304

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