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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 877 · 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. 1.553 − 508 =
  2. 2.621 − 198 =
  3. 3.550 − 497 =
  4. 4.748 − 687 =
  5. 5.983 − 167 =
  6. 6.927 − 479 =
  7. 7.415 − 368 =
  8. 8.816 − 548 =
  9. 9.789 − 527 =
  10. 10.872 − 797 =
  11. 11.869 − 597 =
  12. 12.872 − 699 =
  13. 13.591 − 499 =
  14. 14.836 − 598 =
  15. 15.625 − 579 =
  16. 16.876 − 298 =
  17. 17.994 − 699 =
  18. 18.846 − 617 =
  19. 19.806 − 358 =
  20. 20.751 − 209 =
  21. 21.871 − 397 =
  22. 22.958 − 797 =
  23. 23.645 − 197 =
  24. 24.743 − 699 =
  25. 25.762 − 498 =
  26. 26.812 − 498 =
  27. 27.560 − 197 =
  28. 28.630 − 598 =
  29. 29.658 − 197 =
  30. 30.253 − 117 =
  31. 31.713 − 699 =
  32. 32.525 − 399 =
  33. 33.553 − 498 =
  34. 34.667 − 558 =
  35. 35.836 − 797 =
  36. 36.449 − 289 =
  37. 37.516 − 299 =
  38. 38.707 − 628 =
  39. 39.238 − 169 =
  40. 40.756 − 459 =

Answer key

  1. 45
  2. 423
  3. 53
  4. 61
  5. 816
  6. 448
  7. 47
  8. 268
  9. 262
  10. 75
  11. 272
  12. 173
  13. 92
  14. 238
  15. 46
  16. 578
  17. 295
  18. 229
  19. 448
  20. 542
  21. 474
  22. 161
  23. 448
  24. 44
  25. 264
  26. 314
  27. 363
  28. 32
  29. 461
  30. 136
  31. 14
  32. 126
  33. 55
  34. 109
  35. 39
  36. 160
  37. 217
  38. 79
  39. 69
  40. 297

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