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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 395 · 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. 1.664 − 638 =
  2. 2.724 − 288 =
  3. 3.835 − 699 =
  4. 4.866 − 799 =
  5. 5.350 − 318 =
  6. 6.980 − 599 =
  7. 7.452 − 399 =
  8. 8.369 − 299 =
  9. 9.658 − 598 =
  10. 10.909 − 669 =
  11. 11.641 − 537 =
  12. 12.754 − 467 =
  13. 13.787 − 699 =
  14. 14.737 − 509 =
  15. 15.224 − 197 =
  16. 16.985 − 498 =
  17. 17.311 − 197 =
  18. 18.596 − 298 =
  19. 19.954 − 677 =
  20. 20.927 − 598 =
  21. 21.480 − 448 =
  22. 22.928 − 117 =
  23. 23.275 − 237 =
  24. 24.596 − 347 =
  25. 25.877 − 188 =
  26. 26.239 − 168 =
  27. 27.818 − 538 =
  28. 28.764 − 499 =
  29. 29.792 − 619 =
  30. 30.555 − 217 =
  31. 31.418 − 149 =
  32. 32.351 − 199 =
  33. 33.673 − 637 =
  34. 34.612 − 297 =
  35. 35.768 − 498 =
  36. 36.828 − 697 =
  37. 37.482 − 207 =
  38. 38.928 − 217 =
  39. 39.671 − 599 =
  40. 40.978 − 348 =

Answer key

  1. 26
  2. 436
  3. 136
  4. 67
  5. 32
  6. 381
  7. 53
  8. 70
  9. 60
  10. 240
  11. 104
  12. 287
  13. 88
  14. 228
  15. 27
  16. 487
  17. 114
  18. 298
  19. 277
  20. 329
  21. 32
  22. 811
  23. 38
  24. 249
  25. 689
  26. 71
  27. 280
  28. 265
  29. 173
  30. 338
  31. 269
  32. 152
  33. 36
  34. 315
  35. 270
  36. 131
  37. 275
  38. 711
  39. 72
  40. 630

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