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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 441 · 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. 1.904 − 287 =
  2. 2.586 − 197 =
  3. 3.530 − 428 =
  4. 4.888 − 799 =
  5. 5.896 − 597 =
  6. 6.410 − 349 =
  7. 7.910 − 299 =
  8. 8.632 − 199 =
  9. 9.700 − 577 =
  10. 10.770 − 539 =
  11. 11.716 − 698 =
  12. 12.626 − 427 =
  13. 13.810 − 198 =
  14. 14.862 − 699 =
  15. 15.928 − 609 =
  16. 16.195 − 148 =
  17. 17.362 − 238 =
  18. 18.973 − 597 =
  19. 19.762 − 269 =
  20. 20.549 − 308 =
  21. 21.675 − 398 =
  22. 22.532 − 339 =
  23. 23.280 − 257 =
  24. 24.527 − 469 =
  25. 25.244 − 198 =
  26. 26.984 − 197 =
  27. 27.348 − 297 =
  28. 28.795 − 349 =
  29. 29.778 − 287 =
  30. 30.640 − 199 =
  31. 31.625 − 497 =
  32. 32.631 − 298 =
  33. 33.417 − 358 =
  34. 34.576 − 197 =
  35. 35.790 − 299 =
  36. 36.944 − 697 =
  37. 37.857 − 797 =
  38. 38.335 − 297 =
  39. 39.663 − 297 =
  40. 40.747 − 597 =

Answer key

  1. 617
  2. 389
  3. 102
  4. 89
  5. 299
  6. 61
  7. 611
  8. 433
  9. 123
  10. 231
  11. 18
  12. 199
  13. 612
  14. 163
  15. 319
  16. 47
  17. 124
  18. 376
  19. 493
  20. 241
  21. 277
  22. 193
  23. 23
  24. 58
  25. 46
  26. 787
  27. 51
  28. 446
  29. 491
  30. 441
  31. 128
  32. 333
  33. 59
  34. 379
  35. 491
  36. 247
  37. 60
  38. 38
  39. 366
  40. 150

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