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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 214 · 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. 1.723 − 398 =
  2. 2.534 − 497 =
  3. 3.848 − 798 =
  4. 4.564 − 368 =
  5. 5.500 − 299 =
  6. 6.906 − 487 =
  7. 7.595 − 499 =
  8. 8.466 − 299 =
  9. 9.712 − 399 =
  10. 10.577 − 538 =
  11. 11.611 − 309 =
  12. 12.670 − 519 =
  13. 13.940 − 198 =
  14. 14.674 − 588 =
  15. 15.297 − 199 =
  16. 16.574 − 267 =
  17. 17.900 − 797 =
  18. 18.686 − 639 =
  19. 19.345 − 328 =
  20. 20.817 − 597 =
  21. 21.792 − 697 =
  22. 22.858 − 607 =
  23. 23.858 − 448 =
  24. 24.374 − 199 =
  25. 25.879 − 598 =
  26. 26.771 − 498 =
  27. 27.756 − 397 =
  28. 28.714 − 337 =
  29. 29.802 − 498 =
  30. 30.481 − 439 =
  31. 31.949 − 449 =
  32. 32.892 − 588 =
  33. 33.593 − 508 =
  34. 34.876 − 688 =
  35. 35.873 − 797 =
  36. 36.768 − 289 =
  37. 37.902 − 799 =
  38. 38.774 − 419 =
  39. 39.504 − 398 =
  40. 40.625 − 487 =

Answer key

  1. 325
  2. 37
  3. 50
  4. 196
  5. 201
  6. 419
  7. 96
  8. 167
  9. 313
  10. 39
  11. 302
  12. 151
  13. 742
  14. 86
  15. 98
  16. 307
  17. 103
  18. 47
  19. 17
  20. 220
  21. 95
  22. 251
  23. 410
  24. 175
  25. 281
  26. 273
  27. 359
  28. 377
  29. 304
  30. 42
  31. 500
  32. 304
  33. 85
  34. 188
  35. 76
  36. 479
  37. 103
  38. 355
  39. 106
  40. 138

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