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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 37 · 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. 1.434 − 318 =
  2. 2.724 − 699 =
  3. 3.306 − 208 =
  4. 4.798 − 198 =
  5. 5.976 − 467 =
  6. 6.957 − 697 =
  7. 7.825 − 379 =
  8. 8.518 − 399 =
  9. 9.671 − 549 =
  10. 10.618 − 297 =
  11. 11.918 − 149 =
  12. 12.602 − 198 =
  13. 13.442 − 378 =
  14. 14.918 − 698 =
  15. 15.912 − 699 =
  16. 16.600 − 498 =
  17. 17.534 − 398 =
  18. 18.856 − 798 =
  19. 19.530 − 489 =
  20. 20.577 − 197 =
  21. 21.380 − 238 =
  22. 22.837 − 598 =
  23. 23.870 − 398 =
  24. 24.420 − 198 =
  25. 25.943 − 458 =
  26. 26.645 − 229 =
  27. 27.836 − 797 =
  28. 28.929 − 528 =
  29. 29.255 − 198 =
  30. 30.842 − 799 =
  31. 31.323 − 199 =
  32. 32.652 − 198 =
  33. 33.886 − 579 =
  34. 34.781 − 649 =
  35. 35.354 − 179 =
  36. 36.504 − 368 =
  37. 37.771 − 117 =
  38. 38.885 − 799 =
  39. 39.850 − 798 =
  40. 40.792 − 407 =

Answer key

  1. 116
  2. 25
  3. 98
  4. 600
  5. 509
  6. 260
  7. 446
  8. 119
  9. 122
  10. 321
  11. 769
  12. 404
  13. 64
  14. 220
  15. 213
  16. 102
  17. 136
  18. 58
  19. 41
  20. 380
  21. 142
  22. 239
  23. 472
  24. 222
  25. 485
  26. 416
  27. 39
  28. 401
  29. 57
  30. 43
  31. 124
  32. 454
  33. 307
  34. 132
  35. 175
  36. 136
  37. 654
  38. 86
  39. 52
  40. 385

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