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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 896 · 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. 1.764 − 298 =
  2. 2.990 − 299 =
  3. 3.326 − 297 =
  4. 4.938 − 499 =
  5. 5.650 − 267 =
  6. 6.391 − 198 =
  7. 7.276 − 197 =
  8. 8.552 − 197 =
  9. 9.475 − 438 =
  10. 10.489 − 297 =
  11. 11.384 − 368 =
  12. 12.963 − 397 =
  13. 13.830 − 697 =
  14. 14.605 − 538 =
  15. 15.273 − 117 =
  16. 16.994 − 499 =
  17. 17.546 − 299 =
  18. 18.727 − 299 =
  19. 19.355 − 298 =
  20. 20.726 − 618 =
  21. 21.313 − 297 =
  22. 22.421 − 199 =
  23. 23.964 − 299 =
  24. 24.978 − 547 =
  25. 25.666 − 497 =
  26. 26.437 − 398 =
  27. 27.745 − 209 =
  28. 28.644 − 528 =
  29. 29.622 − 569 =
  30. 30.605 − 429 =
  31. 31.930 − 797 =
  32. 32.826 − 508 =
  33. 33.295 − 209 =
  34. 34.897 − 399 =
  35. 35.534 − 397 =
  36. 36.741 − 399 =
  37. 37.883 − 157 =
  38. 38.597 − 497 =
  39. 39.236 − 197 =
  40. 40.557 − 398 =

Answer key

  1. 466
  2. 691
  3. 29
  4. 439
  5. 383
  6. 193
  7. 79
  8. 355
  9. 37
  10. 192
  11. 16
  12. 566
  13. 133
  14. 67
  15. 156
  16. 495
  17. 247
  18. 428
  19. 57
  20. 108
  21. 16
  22. 222
  23. 665
  24. 431
  25. 169
  26. 39
  27. 536
  28. 116
  29. 53
  30. 176
  31. 133
  32. 318
  33. 86
  34. 498
  35. 137
  36. 342
  37. 726
  38. 100
  39. 39
  40. 159

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