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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 790 · 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. 1.676 − 608 =
  2. 2.485 − 199 =
  3. 3.724 − 669 =
  4. 4.817 − 397 =
  5. 5.882 − 299 =
  6. 6.514 − 299 =
  7. 7.772 − 469 =
  8. 8.827 − 699 =
  9. 9.468 − 298 =
  10. 10.665 − 397 =
  11. 11.559 − 299 =
  12. 12.433 − 299 =
  13. 13.674 − 639 =
  14. 14.418 − 379 =
  15. 15.304 − 199 =
  16. 16.907 − 797 =
  17. 17.717 − 627 =
  18. 18.249 − 197 =
  19. 19.747 − 209 =
  20. 20.256 − 167 =
  21. 21.753 − 699 =
  22. 22.864 − 267 =
  23. 23.755 − 598 =
  24. 24.723 − 498 =
  25. 25.770 − 599 =
  26. 26.857 − 699 =
  27. 27.806 − 399 =
  28. 28.939 − 197 =
  29. 29.618 − 499 =
  30. 30.850 − 407 =
  31. 31.888 − 547 =
  32. 32.800 − 159 =
  33. 33.778 − 478 =
  34. 34.435 − 397 =
  35. 35.699 − 117 =
  36. 36.709 − 448 =
  37. 37.977 − 248 =
  38. 38.757 − 338 =
  39. 39.760 − 628 =
  40. 40.798 − 197 =

Answer key

  1. 68
  2. 286
  3. 55
  4. 420
  5. 583
  6. 215
  7. 303
  8. 128
  9. 170
  10. 268
  11. 260
  12. 134
  13. 35
  14. 39
  15. 105
  16. 110
  17. 90
  18. 52
  19. 538
  20. 89
  21. 54
  22. 597
  23. 157
  24. 225
  25. 171
  26. 158
  27. 407
  28. 742
  29. 119
  30. 443
  31. 341
  32. 641
  33. 300
  34. 38
  35. 582
  36. 261
  37. 729
  38. 419
  39. 132
  40. 601

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