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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 241 · 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. 1.425 − 297 =
  2. 2.851 − 799 =
  3. 3.687 − 609 =
  4. 4.661 − 409 =
  5. 5.737 − 398 =
  6. 6.391 − 199 =
  7. 7.634 − 537 =
  8. 8.755 − 598 =
  9. 9.628 − 429 =
  10. 10.628 − 599 =
  11. 11.488 − 118 =
  12. 12.971 − 348 =
  13. 13.615 − 569 =
  14. 14.530 − 498 =
  15. 15.925 − 798 =
  16. 16.904 − 798 =
  17. 17.865 − 448 =
  18. 18.709 − 668 =
  19. 19.565 − 369 =
  20. 20.966 − 328 =
  21. 21.855 − 798 =
  22. 22.275 − 198 =
  23. 23.324 − 268 =
  24. 24.784 − 539 =
  25. 25.984 − 598 =
  26. 26.896 − 298 =
  27. 27.945 − 697 =
  28. 28.746 − 628 =
  29. 29.948 − 797 =
  30. 30.680 − 298 =
  31. 31.516 − 499 =
  32. 32.844 − 327 =
  33. 33.888 − 798 =
  34. 34.695 − 169 =
  35. 35.873 − 499 =
  36. 36.840 − 398 =
  37. 37.843 − 697 =
  38. 38.917 − 659 =
  39. 39.616 − 497 =
  40. 40.943 − 307 =

Answer key

  1. 128
  2. 52
  3. 78
  4. 252
  5. 339
  6. 192
  7. 97
  8. 157
  9. 199
  10. 29
  11. 370
  12. 623
  13. 46
  14. 32
  15. 127
  16. 106
  17. 417
  18. 41
  19. 196
  20. 638
  21. 57
  22. 77
  23. 56
  24. 245
  25. 386
  26. 598
  27. 248
  28. 118
  29. 151
  30. 382
  31. 17
  32. 517
  33. 90
  34. 526
  35. 374
  36. 442
  37. 146
  38. 258
  39. 119
  40. 636

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