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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 5 · 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. 1.834 − 217 =
  2. 2.551 − 497 =
  3. 3.555 − 469 =
  4. 4.645 − 247 =
  5. 5.614 − 599 =
  6. 6.953 − 799 =
  7. 7.902 − 497 =
  8. 8.726 − 697 =
  9. 9.890 − 579 =
  10. 10.984 − 397 =
  11. 11.788 − 498 =
  12. 12.555 − 217 =
  13. 13.886 − 599 =
  14. 14.527 − 397 =
  15. 15.753 − 499 =
  16. 16.935 − 357 =
  17. 17.874 − 677 =
  18. 18.334 − 278 =
  19. 19.185 − 119 =
  20. 20.969 − 797 =
  21. 21.407 − 369 =
  22. 22.808 − 368 =
  23. 23.696 − 568 =
  24. 24.259 − 179 =
  25. 25.852 − 598 =
  26. 26.987 − 199 =
  27. 27.777 − 398 =
  28. 28.864 − 639 =
  29. 29.607 − 499 =
  30. 30.629 − 198 =
  31. 31.315 − 149 =
  32. 32.941 − 529 =
  33. 33.946 − 509 =
  34. 34.959 − 197 =
  35. 35.465 − 219 =
  36. 36.703 − 588 =
  37. 37.561 − 419 =
  38. 38.754 − 699 =
  39. 39.806 − 308 =
  40. 40.705 − 489 =

Answer key

  1. 617
  2. 54
  3. 86
  4. 398
  5. 15
  6. 154
  7. 405
  8. 29
  9. 311
  10. 587
  11. 290
  12. 338
  13. 287
  14. 130
  15. 254
  16. 578
  17. 197
  18. 56
  19. 66
  20. 172
  21. 38
  22. 440
  23. 128
  24. 80
  25. 254
  26. 788
  27. 379
  28. 225
  29. 108
  30. 431
  31. 166
  32. 412
  33. 437
  34. 762
  35. 246
  36. 115
  37. 142
  38. 55
  39. 498
  40. 216

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