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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 729 · 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. 1.576 − 248 =
  2. 2.742 − 699 =
  3. 3.905 − 399 =
  4. 4.553 − 487 =
  5. 5.768 − 698 =
  6. 6.953 − 697 =
  7. 7.664 − 489 =
  8. 8.725 − 698 =
  9. 9.883 − 599 =
  10. 10.821 − 799 =
  11. 11.640 − 397 =
  12. 12.615 − 297 =
  13. 13.598 − 148 =
  14. 14.912 − 657 =
  15. 15.350 − 199 =
  16. 16.483 − 337 =
  17. 17.883 − 347 =
  18. 18.533 − 398 =
  19. 19.705 − 529 =
  20. 20.331 − 298 =
  21. 21.951 − 418 =
  22. 22.816 − 368 =
  23. 23.524 − 499 =
  24. 24.625 − 318 =
  25. 25.470 − 297 =
  26. 26.512 − 327 =
  27. 27.901 − 297 =
  28. 28.860 − 398 =
  29. 29.324 − 197 =
  30. 30.321 − 198 =
  31. 31.437 − 379 =
  32. 32.452 − 398 =
  33. 33.614 − 597 =
  34. 34.874 − 497 =
  35. 35.698 − 177 =
  36. 36.931 − 358 =
  37. 37.385 − 308 =
  38. 38.843 − 587 =
  39. 39.454 − 398 =
  40. 40.910 − 499 =

Answer key

  1. 328
  2. 43
  3. 506
  4. 66
  5. 70
  6. 256
  7. 175
  8. 27
  9. 284
  10. 22
  11. 243
  12. 318
  13. 450
  14. 255
  15. 151
  16. 146
  17. 536
  18. 135
  19. 176
  20. 33
  21. 533
  22. 448
  23. 25
  24. 307
  25. 173
  26. 185
  27. 604
  28. 462
  29. 127
  30. 123
  31. 58
  32. 54
  33. 17
  34. 377
  35. 521
  36. 573
  37. 77
  38. 256
  39. 56
  40. 411

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