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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 210 · 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. 1.569 − 497 =
  2. 2.575 − 339 =
  3. 3.846 − 497 =
  4. 4.729 − 697 =
  5. 5.558 − 437 =
  6. 6.338 − 198 =
  7. 7.770 − 497 =
  8. 8.948 − 499 =
  9. 9.949 − 667 =
  10. 10.665 − 299 =
  11. 11.950 − 637 =
  12. 12.610 − 577 =
  13. 13.664 − 298 =
  14. 14.673 − 398 =
  15. 15.995 − 479 =
  16. 16.562 − 489 =
  17. 17.453 − 248 =
  18. 18.964 − 397 =
  19. 19.693 − 599 =
  20. 20.550 − 487 =
  21. 21.522 − 268 =
  22. 22.652 − 597 =
  23. 23.677 − 597 =
  24. 24.892 − 299 =
  25. 25.882 − 799 =
  26. 26.576 − 399 =
  27. 27.385 − 297 =
  28. 28.395 − 298 =
  29. 29.780 − 197 =
  30. 30.490 − 399 =
  31. 31.974 − 669 =
  32. 32.982 − 649 =
  33. 33.847 − 697 =
  34. 34.808 − 698 =
  35. 35.912 − 497 =
  36. 36.423 − 378 =
  37. 37.910 − 798 =
  38. 38.992 − 799 =
  39. 39.820 − 347 =
  40. 40.791 − 468 =

Answer key

  1. 72
  2. 236
  3. 349
  4. 32
  5. 121
  6. 140
  7. 273
  8. 449
  9. 282
  10. 366
  11. 313
  12. 33
  13. 366
  14. 275
  15. 516
  16. 73
  17. 205
  18. 567
  19. 94
  20. 63
  21. 254
  22. 55
  23. 80
  24. 593
  25. 83
  26. 177
  27. 88
  28. 97
  29. 583
  30. 91
  31. 305
  32. 333
  33. 150
  34. 110
  35. 415
  36. 45
  37. 112
  38. 193
  39. 473
  40. 323

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