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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 510 · 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. 1.433 − 397 =
  2. 2.469 − 298 =
  3. 3.309 − 157 =
  4. 4.299 − 138 =
  5. 5.894 − 677 =
  6. 6.658 − 299 =
  7. 7.393 − 299 =
  8. 8.702 − 418 =
  9. 9.965 − 199 =
  10. 10.575 − 299 =
  11. 11.357 − 297 =
  12. 12.640 − 387 =
  13. 13.915 − 198 =
  14. 14.652 − 217 =
  15. 15.887 − 199 =
  16. 16.306 − 269 =
  17. 17.767 − 698 =
  18. 18.682 − 617 =
  19. 19.822 − 798 =
  20. 20.897 − 699 =
  21. 21.932 − 799 =
  22. 22.712 − 378 =
  23. 23.637 − 599 =
  24. 24.640 − 398 =
  25. 25.907 − 498 =
  26. 26.326 − 197 =
  27. 27.524 − 499 =
  28. 28.636 − 298 =
  29. 29.588 − 199 =
  30. 30.602 − 498 =
  31. 31.902 − 277 =
  32. 32.758 − 498 =
  33. 33.792 − 169 =
  34. 34.753 − 698 =
  35. 35.395 − 218 =
  36. 36.842 − 599 =
  37. 37.543 − 399 =
  38. 38.735 − 598 =
  39. 39.509 − 177 =
  40. 40.815 − 658 =

Answer key

  1. 36
  2. 171
  3. 152
  4. 161
  5. 217
  6. 359
  7. 94
  8. 284
  9. 766
  10. 276
  11. 60
  12. 253
  13. 717
  14. 435
  15. 688
  16. 37
  17. 69
  18. 65
  19. 24
  20. 198
  21. 133
  22. 334
  23. 38
  24. 242
  25. 409
  26. 129
  27. 25
  28. 338
  29. 389
  30. 104
  31. 625
  32. 260
  33. 623
  34. 55
  35. 177
  36. 243
  37. 144
  38. 137
  39. 332
  40. 157

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