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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 355 · 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. 1.846 − 599 =
  2. 2.825 − 497 =
  3. 3.278 − 218 =
  4. 4.248 − 198 =
  5. 5.758 − 699 =
  6. 6.833 − 799 =
  7. 7.770 − 589 =
  8. 8.784 − 297 =
  9. 9.542 − 497 =
  10. 10.853 − 549 =
  11. 11.906 − 798 =
  12. 12.755 − 427 =
  13. 13.608 − 179 =
  14. 14.359 − 247 =
  15. 15.561 − 487 =
  16. 16.744 − 397 =
  17. 17.875 − 518 =
  18. 18.486 − 428 =
  19. 19.837 − 797 =
  20. 20.616 − 498 =
  21. 21.647 − 588 =
  22. 22.677 − 598 =
  23. 23.559 − 368 =
  24. 24.447 − 298 =
  25. 25.659 − 558 =
  26. 26.776 − 699 =
  27. 27.834 − 497 =
  28. 28.541 − 198 =
  29. 29.584 − 318 =
  30. 30.514 − 347 =
  31. 31.882 − 609 =
  32. 32.921 − 698 =
  33. 33.720 − 538 =
  34. 34.874 − 698 =
  35. 35.686 − 599 =
  36. 36.420 − 238 =
  37. 37.416 − 129 =
  38. 38.580 − 497 =
  39. 39.776 − 139 =
  40. 40.760 − 498 =

Answer key

  1. 247
  2. 328
  3. 60
  4. 50
  5. 59
  6. 34
  7. 181
  8. 487
  9. 45
  10. 304
  11. 108
  12. 328
  13. 429
  14. 112
  15. 74
  16. 347
  17. 357
  18. 58
  19. 40
  20. 118
  21. 59
  22. 79
  23. 191
  24. 149
  25. 101
  26. 77
  27. 337
  28. 343
  29. 266
  30. 167
  31. 273
  32. 223
  33. 182
  34. 176
  35. 87
  36. 182
  37. 287
  38. 83
  39. 637
  40. 262

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