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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 477 · 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. 1.999 − 198 =
  2. 2.572 − 519 =
  3. 3.707 − 657 =
  4. 4.877 − 698 =
  5. 5.630 − 269 =
  6. 6.897 − 448 =
  7. 7.866 − 699 =
  8. 8.694 − 359 =
  9. 9.766 − 697 =
  10. 10.688 − 549 =
  11. 11.839 − 797 =
  12. 12.715 − 399 =
  13. 13.677 − 599 =
  14. 14.941 − 687 =
  15. 15.582 − 498 =
  16. 16.712 − 399 =
  17. 17.590 − 228 =
  18. 18.841 − 497 =
  19. 19.547 − 378 =
  20. 20.457 − 397 =
  21. 21.885 − 797 =
  22. 22.720 − 577 =
  23. 23.714 − 208 =
  24. 24.757 − 398 =
  25. 25.770 − 519 =
  26. 26.809 − 299 =
  27. 27.423 − 409 =
  28. 28.436 − 297 =
  29. 29.757 − 659 =
  30. 30.904 − 628 =
  31. 31.520 − 119 =
  32. 32.901 − 537 =
  33. 33.997 − 609 =
  34. 34.941 − 697 =
  35. 35.769 − 697 =
  36. 36.447 − 198 =
  37. 37.745 − 629 =
  38. 38.906 − 798 =
  39. 39.979 − 578 =
  40. 40.915 − 798 =

Answer key

  1. 801
  2. 53
  3. 50
  4. 179
  5. 361
  6. 449
  7. 167
  8. 335
  9. 69
  10. 139
  11. 42
  12. 316
  13. 78
  14. 254
  15. 84
  16. 313
  17. 362
  18. 344
  19. 169
  20. 60
  21. 88
  22. 143
  23. 506
  24. 359
  25. 251
  26. 510
  27. 14
  28. 139
  29. 98
  30. 276
  31. 401
  32. 364
  33. 388
  34. 244
  35. 72
  36. 249
  37. 116
  38. 108
  39. 401
  40. 117

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