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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 224 · 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. 1.686 − 218 =
  2. 2.475 − 239 =
  3. 3.842 − 597 =
  4. 4.707 − 659 =
  5. 5.697 − 597 =
  6. 6.711 − 198 =
  7. 7.663 − 597 =
  8. 8.839 − 498 =
  9. 9.819 − 519 =
  10. 10.666 − 537 =
  11. 11.891 − 299 =
  12. 12.810 − 397 =
  13. 13.875 − 797 =
  14. 14.425 − 347 =
  15. 15.543 − 419 =
  16. 16.916 − 597 =
  17. 17.158 − 138 =
  18. 18.650 − 579 =
  19. 19.644 − 198 =
  20. 20.805 − 498 =
  21. 21.730 − 698 =
  22. 22.935 − 799 =
  23. 23.775 − 369 =
  24. 24.838 − 197 =
  25. 25.881 − 798 =
  26. 26.465 − 397 =
  27. 27.987 − 549 =
  28. 28.656 − 199 =
  29. 29.379 − 318 =
  30. 30.667 − 629 =
  31. 31.729 − 598 =
  32. 32.398 − 199 =
  33. 33.775 − 298 =
  34. 34.485 − 439 =
  35. 35.892 − 248 =
  36. 36.444 − 248 =
  37. 37.512 − 499 =
  38. 38.729 − 399 =
  39. 39.438 − 287 =
  40. 40.868 − 798 =

Answer key

  1. 468
  2. 236
  3. 245
  4. 48
  5. 100
  6. 513
  7. 66
  8. 341
  9. 300
  10. 129
  11. 592
  12. 413
  13. 78
  14. 78
  15. 124
  16. 319
  17. 20
  18. 71
  19. 446
  20. 307
  21. 32
  22. 136
  23. 406
  24. 641
  25. 83
  26. 68
  27. 438
  28. 457
  29. 61
  30. 38
  31. 131
  32. 199
  33. 477
  34. 46
  35. 644
  36. 196
  37. 13
  38. 330
  39. 151
  40. 70

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