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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 902 · 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. 1.748 − 149 =
  2. 2.376 − 169 =
  3. 3.579 − 199 =
  4. 4.647 − 399 =
  5. 5.846 − 397 =
  6. 6.248 − 197 =
  7. 7.610 − 298 =
  8. 8.597 − 199 =
  9. 9.651 − 147 =
  10. 10.732 − 169 =
  11. 11.579 − 217 =
  12. 12.376 − 199 =
  13. 13.733 − 388 =
  14. 14.251 − 157 =
  15. 15.568 − 398 =
  16. 16.835 − 689 =
  17. 17.526 − 397 =
  18. 18.271 − 148 =
  19. 19.836 − 798 =
  20. 20.375 − 299 =
  21. 21.627 − 597 =
  22. 22.946 − 477 =
  23. 23.828 − 197 =
  24. 24.387 − 299 =
  25. 25.923 − 218 =
  26. 26.777 − 699 =
  27. 27.877 − 599 =
  28. 28.843 − 798 =
  29. 29.848 − 799 =
  30. 30.531 − 197 =
  31. 31.621 − 498 =
  32. 32.634 − 279 =
  33. 33.844 − 677 =
  34. 34.728 − 497 =
  35. 35.534 − 498 =
  36. 36.443 − 197 =
  37. 37.985 − 797 =
  38. 38.667 − 598 =
  39. 39.850 − 698 =
  40. 40.508 − 297 =

Answer key

  1. 599
  2. 207
  3. 380
  4. 248
  5. 449
  6. 51
  7. 312
  8. 398
  9. 504
  10. 563
  11. 362
  12. 177
  13. 345
  14. 94
  15. 170
  16. 146
  17. 129
  18. 123
  19. 38
  20. 76
  21. 30
  22. 469
  23. 631
  24. 88
  25. 705
  26. 78
  27. 278
  28. 45
  29. 49
  30. 334
  31. 123
  32. 355
  33. 167
  34. 231
  35. 36
  36. 246
  37. 188
  38. 69
  39. 152
  40. 211

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