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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 446 · 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. 1.633 − 358 =
  2. 2.895 − 797 =
  3. 3.979 − 798 =
  4. 4.924 − 597 =
  5. 5.759 − 597 =
  6. 6.741 − 397 =
  7. 7.900 − 419 =
  8. 8.674 − 197 =
  9. 9.722 − 549 =
  10. 10.391 − 337 =
  11. 11.969 − 798 =
  12. 12.922 − 798 =
  13. 13.478 − 159 =
  14. 14.258 − 229 =
  15. 15.685 − 297 =
  16. 16.458 − 347 =
  17. 17.799 − 699 =
  18. 18.994 − 207 =
  19. 19.599 − 577 =
  20. 20.693 − 579 =
  21. 21.949 − 597 =
  22. 22.770 − 497 =
  23. 23.943 − 498 =
  24. 24.401 − 287 =
  25. 25.944 − 798 =
  26. 26.900 − 699 =
  27. 27.871 − 299 =
  28. 28.495 − 397 =
  29. 29.593 − 399 =
  30. 30.749 − 677 =
  31. 31.991 − 337 =
  32. 32.775 − 328 =
  33. 33.997 − 397 =
  34. 34.937 − 797 =
  35. 35.476 − 397 =
  36. 36.737 − 597 =
  37. 37.668 − 238 =
  38. 38.824 − 797 =
  39. 39.986 − 298 =
  40. 40.626 − 197 =

Answer key

  1. 275
  2. 98
  3. 181
  4. 327
  5. 162
  6. 344
  7. 481
  8. 477
  9. 173
  10. 54
  11. 171
  12. 124
  13. 319
  14. 29
  15. 388
  16. 111
  17. 100
  18. 787
  19. 22
  20. 114
  21. 352
  22. 273
  23. 445
  24. 114
  25. 146
  26. 201
  27. 572
  28. 98
  29. 194
  30. 72
  31. 654
  32. 447
  33. 600
  34. 140
  35. 79
  36. 140
  37. 430
  38. 27
  39. 688
  40. 429

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