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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 165 · 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. 1.726 − 497 =
  2. 2.461 − 297 =
  3. 3.209 − 148 =
  4. 4.979 − 297 =
  5. 5.524 − 429 =
  6. 6.884 − 528 =
  7. 7.867 − 799 =
  8. 8.914 − 477 =
  9. 9.633 − 537 =
  10. 10.367 − 189 =
  11. 11.893 − 317 =
  12. 12.611 − 497 =
  13. 13.882 − 798 =
  14. 14.405 − 198 =
  15. 15.835 − 797 =
  16. 16.991 − 797 =
  17. 17.863 − 609 =
  18. 18.599 − 567 =
  19. 19.533 − 197 =
  20. 20.748 − 539 =
  21. 21.871 − 498 =
  22. 22.964 − 289 =
  23. 23.883 − 799 =
  24. 24.365 − 249 =
  25. 25.712 − 597 =
  26. 26.761 − 619 =
  27. 27.631 − 558 =
  28. 28.550 − 398 =
  29. 29.599 − 199 =
  30. 30.396 − 348 =
  31. 31.828 − 799 =
  32. 32.634 − 399 =
  33. 33.310 − 197 =
  34. 34.955 − 299 =
  35. 35.878 − 697 =
  36. 36.550 − 519 =
  37. 37.624 − 599 =
  38. 38.824 − 479 =
  39. 39.960 − 697 =
  40. 40.392 − 299 =

Answer key

  1. 229
  2. 164
  3. 61
  4. 682
  5. 95
  6. 356
  7. 68
  8. 437
  9. 96
  10. 178
  11. 576
  12. 114
  13. 84
  14. 207
  15. 38
  16. 194
  17. 254
  18. 32
  19. 336
  20. 209
  21. 373
  22. 675
  23. 84
  24. 116
  25. 115
  26. 142
  27. 73
  28. 152
  29. 400
  30. 48
  31. 29
  32. 235
  33. 113
  34. 656
  35. 181
  36. 31
  37. 25
  38. 345
  39. 263
  40. 93

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