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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 254 · 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. 1.641 − 498 =
  2. 2.523 − 198 =
  3. 3.764 − 687 =
  4. 4.752 − 499 =
  5. 5.258 − 199 =
  6. 6.558 − 379 =
  7. 7.414 − 397 =
  8. 8.578 − 288 =
  9. 9.838 − 248 =
  10. 10.746 − 699 =
  11. 11.974 − 597 =
  12. 12.572 − 397 =
  13. 13.486 − 217 =
  14. 14.717 − 537 =
  15. 15.659 − 307 =
  16. 16.815 − 438 =
  17. 17.462 − 208 =
  18. 18.427 − 189 =
  19. 19.947 − 298 =
  20. 20.464 − 219 =
  21. 21.393 − 299 =
  22. 22.715 − 649 =
  23. 23.539 − 247 =
  24. 24.743 − 499 =
  25. 25.409 − 297 =
  26. 26.866 − 198 =
  27. 27.439 − 199 =
  28. 28.992 − 647 =
  29. 29.672 − 397 =
  30. 30.965 − 288 =
  31. 31.721 − 297 =
  32. 32.935 − 297 =
  33. 33.792 − 479 =
  34. 34.716 − 297 =
  35. 35.655 − 199 =
  36. 36.970 − 577 =
  37. 37.823 − 699 =
  38. 38.694 − 617 =
  39. 39.763 − 628 =
  40. 40.635 − 397 =

Answer key

  1. 143
  2. 325
  3. 77
  4. 253
  5. 59
  6. 179
  7. 17
  8. 290
  9. 590
  10. 47
  11. 377
  12. 175
  13. 269
  14. 180
  15. 352
  16. 377
  17. 254
  18. 238
  19. 649
  20. 245
  21. 94
  22. 66
  23. 292
  24. 244
  25. 112
  26. 668
  27. 240
  28. 345
  29. 275
  30. 677
  31. 424
  32. 638
  33. 313
  34. 419
  35. 456
  36. 393
  37. 124
  38. 77
  39. 135
  40. 238

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