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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 397 · 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. 1.847 − 538 =
  2. 2.983 − 598 =
  3. 3.713 − 598 =
  4. 4.950 − 497 =
  5. 5.748 − 409 =
  6. 6.980 − 199 =
  7. 7.505 − 399 =
  8. 8.327 − 198 =
  9. 9.777 − 389 =
  10. 10.757 − 298 =
  11. 11.619 − 468 =
  12. 12.981 − 497 =
  13. 13.996 − 208 =
  14. 14.679 − 619 =
  15. 15.622 − 197 =
  16. 16.880 − 197 =
  17. 17.834 − 678 =
  18. 18.311 − 198 =
  19. 19.850 − 588 =
  20. 20.816 − 697 =
  21. 21.534 − 207 =
  22. 22.906 − 798 =
  23. 23.957 − 797 =
  24. 24.679 − 257 =
  25. 25.675 − 619 =
  26. 26.702 − 299 =
  27. 27.782 − 599 =
  28. 28.974 − 697 =
  29. 29.939 − 569 =
  30. 30.886 − 179 =
  31. 31.852 − 797 =
  32. 32.964 − 389 =
  33. 33.537 − 308 =
  34. 34.243 − 128 =
  35. 35.937 − 797 =
  36. 36.636 − 497 =
  37. 37.254 − 207 =
  38. 38.762 − 699 =
  39. 39.436 − 207 =
  40. 40.739 − 697 =

Answer key

  1. 309
  2. 385
  3. 115
  4. 453
  5. 339
  6. 781
  7. 106
  8. 129
  9. 388
  10. 459
  11. 151
  12. 484
  13. 788
  14. 60
  15. 425
  16. 683
  17. 156
  18. 113
  19. 262
  20. 119
  21. 327
  22. 108
  23. 160
  24. 422
  25. 56
  26. 403
  27. 183
  28. 277
  29. 370
  30. 707
  31. 55
  32. 575
  33. 229
  34. 115
  35. 140
  36. 139
  37. 47
  38. 63
  39. 229
  40. 42

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