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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 150 · 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. 1.471 − 299 =
  2. 2.792 − 678 =
  3. 3.725 − 227 =
  4. 4.800 − 398 =
  5. 5.968 − 697 =
  6. 6.825 − 497 =
  7. 7.714 − 649 =
  8. 8.839 − 798 =
  9. 9.918 − 419 =
  10. 10.353 − 299 =
  11. 11.576 − 329 =
  12. 12.764 − 499 =
  13. 13.936 − 117 =
  14. 14.205 − 178 =
  15. 15.636 − 337 =
  16. 16.684 − 628 =
  17. 17.578 − 489 =
  18. 18.747 − 597 =
  19. 19.922 − 578 =
  20. 20.355 − 247 =
  21. 21.965 − 498 =
  22. 22.812 − 697 =
  23. 23.503 − 339 =
  24. 24.754 − 699 =
  25. 25.740 − 698 =
  26. 26.690 − 567 =
  27. 27.418 − 387 =
  28. 28.995 − 548 =
  29. 29.736 − 698 =
  30. 30.719 − 677 =
  31. 31.476 − 369 =
  32. 32.730 − 388 =
  33. 33.534 − 227 =
  34. 34.833 − 597 =
  35. 35.722 − 618 =
  36. 36.169 − 139 =
  37. 37.309 − 237 =
  38. 38.546 − 267 =
  39. 39.980 − 198 =
  40. 40.675 − 538 =

Answer key

  1. 172
  2. 114
  3. 498
  4. 402
  5. 271
  6. 328
  7. 65
  8. 41
  9. 499
  10. 54
  11. 247
  12. 265
  13. 819
  14. 27
  15. 299
  16. 56
  17. 89
  18. 150
  19. 344
  20. 108
  21. 467
  22. 115
  23. 164
  24. 55
  25. 42
  26. 123
  27. 31
  28. 447
  29. 38
  30. 42
  31. 107
  32. 342
  33. 307
  34. 236
  35. 104
  36. 30
  37. 72
  38. 279
  39. 782
  40. 137

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