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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 487 · 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. 1.891 − 798 =
  2. 2.589 − 199 =
  3. 3.754 − 629 =
  4. 4.707 − 639 =
  5. 5.741 − 197 =
  6. 6.867 − 797 =
  7. 7.758 − 297 =
  8. 8.824 − 559 =
  9. 9.852 − 577 =
  10. 10.943 − 198 =
  11. 11.808 − 599 =
  12. 12.818 − 327 =
  13. 13.578 − 498 =
  14. 14.743 − 298 =
  15. 15.943 − 277 =
  16. 16.841 − 297 =
  17. 17.854 − 277 =
  18. 18.975 − 158 =
  19. 19.277 − 199 =
  20. 20.778 − 498 =
  21. 21.435 − 299 =
  22. 22.679 − 647 =
  23. 23.941 − 398 =
  24. 24.562 − 299 =
  25. 25.736 − 698 =
  26. 26.670 − 588 =
  27. 27.917 − 299 =
  28. 28.608 − 499 =
  29. 29.818 − 399 =
  30. 30.739 − 178 =
  31. 31.444 − 197 =
  32. 32.905 − 797 =
  33. 33.568 − 478 =
  34. 34.226 − 188 =
  35. 35.214 − 187 =
  36. 36.850 − 798 =
  37. 37.859 − 408 =
  38. 38.966 − 279 =
  39. 39.987 − 797 =
  40. 40.461 − 297 =

Answer key

  1. 93
  2. 390
  3. 125
  4. 68
  5. 544
  6. 70
  7. 461
  8. 265
  9. 275
  10. 745
  11. 209
  12. 491
  13. 80
  14. 445
  15. 666
  16. 544
  17. 577
  18. 817
  19. 78
  20. 280
  21. 136
  22. 32
  23. 543
  24. 263
  25. 38
  26. 82
  27. 618
  28. 109
  29. 419
  30. 561
  31. 247
  32. 108
  33. 90
  34. 38
  35. 27
  36. 52
  37. 451
  38. 687
  39. 190
  40. 164

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