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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 95 · 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. 1.887 − 798 =
  2. 2.785 − 599 =
  3. 3.909 − 367 =
  4. 4.915 − 417 =
  5. 5.783 − 598 =
  6. 6.671 − 558 =
  7. 7.543 − 499 =
  8. 8.789 − 339 =
  9. 9.413 − 329 =
  10. 10.907 − 448 =
  11. 11.755 − 689 =
  12. 12.707 − 497 =
  13. 13.433 − 267 =
  14. 14.576 − 467 =
  15. 15.348 − 197 =
  16. 16.793 − 547 =
  17. 17.971 − 667 =
  18. 18.827 − 498 =
  19. 19.971 − 297 =
  20. 20.953 − 378 =
  21. 21.748 − 609 =
  22. 22.917 − 697 =
  23. 23.988 − 598 =
  24. 24.522 − 297 =
  25. 25.603 − 569 =
  26. 26.615 − 498 =
  27. 27.676 − 397 =
  28. 28.214 − 199 =
  29. 29.474 − 359 =
  30. 30.937 − 798 =
  31. 31.826 − 797 =
  32. 32.693 − 229 =
  33. 33.884 − 797 =
  34. 34.264 − 199 =
  35. 35.308 − 197 =
  36. 36.747 − 599 =
  37. 37.635 − 439 =
  38. 38.580 − 517 =
  39. 39.699 − 499 =
  40. 40.705 − 457 =

Answer key

  1. 89
  2. 186
  3. 542
  4. 498
  5. 185
  6. 113
  7. 44
  8. 450
  9. 84
  10. 459
  11. 66
  12. 210
  13. 166
  14. 109
  15. 151
  16. 246
  17. 304
  18. 329
  19. 674
  20. 575
  21. 139
  22. 220
  23. 390
  24. 225
  25. 34
  26. 117
  27. 279
  28. 15
  29. 115
  30. 139
  31. 29
  32. 464
  33. 87
  34. 65
  35. 111
  36. 148
  37. 196
  38. 63
  39. 200
  40. 248

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