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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 126 · 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. 1.815 − 799 =
  2. 2.980 − 379 =
  3. 3.780 − 698 =
  4. 4.779 − 499 =
  5. 5.879 − 397 =
  6. 6.380 − 119 =
  7. 7.394 − 197 =
  8. 8.924 − 217 =
  9. 9.527 − 498 =
  10. 10.788 − 599 =
  11. 11.588 − 299 =
  12. 12.824 − 609 =
  13. 13.826 − 219 =
  14. 14.366 − 297 =
  15. 15.879 − 649 =
  16. 16.744 − 698 =
  17. 17.582 − 197 =
  18. 18.419 − 197 =
  19. 19.937 − 657 =
  20. 20.423 − 397 =
  21. 21.682 − 499 =
  22. 22.821 − 599 =
  23. 23.372 − 199 =
  24. 24.440 − 418 =
  25. 25.981 − 797 =
  26. 26.916 − 188 =
  27. 27.608 − 199 =
  28. 28.767 − 299 =
  29. 29.623 − 197 =
  30. 30.674 − 598 =
  31. 31.844 − 598 =
  32. 32.625 − 598 =
  33. 33.716 − 577 =
  34. 34.635 − 249 =
  35. 35.680 − 199 =
  36. 36.642 − 168 =
  37. 37.618 − 119 =
  38. 38.966 − 288 =
  39. 39.817 − 498 =
  40. 40.926 − 798 =

Answer key

  1. 16
  2. 601
  3. 82
  4. 280
  5. 482
  6. 261
  7. 197
  8. 707
  9. 29
  10. 189
  11. 289
  12. 215
  13. 607
  14. 69
  15. 230
  16. 46
  17. 385
  18. 222
  19. 280
  20. 26
  21. 183
  22. 222
  23. 173
  24. 22
  25. 184
  26. 728
  27. 409
  28. 468
  29. 426
  30. 76
  31. 246
  32. 27
  33. 139
  34. 386
  35. 481
  36. 474
  37. 499
  38. 678
  39. 319
  40. 128

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