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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 265 · 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. 1.335 − 199 =
  2. 2.998 − 699 =
  3. 3.568 − 197 =
  4. 4.363 − 137 =
  5. 5.853 − 598 =
  6. 6.668 − 507 =
  7. 7.574 − 399 =
  8. 8.546 − 127 =
  9. 9.859 − 178 =
  10. 10.992 − 198 =
  11. 11.665 − 597 =
  12. 12.938 − 378 =
  13. 13.754 − 699 =
  14. 14.717 − 698 =
  15. 15.315 − 199 =
  16. 16.375 − 297 =
  17. 17.797 − 277 =
  18. 18.964 − 799 =
  19. 19.481 − 398 =
  20. 20.838 − 499 =
  21. 21.547 − 399 =
  22. 22.336 − 299 =
  23. 23.359 − 217 =
  24. 24.991 − 399 =
  25. 25.677 − 657 =
  26. 26.983 − 297 =
  27. 27.911 − 509 =
  28. 28.415 − 398 =
  29. 29.722 − 297 =
  30. 30.815 − 699 =
  31. 31.954 − 498 =
  32. 32.557 − 398 =
  33. 33.666 − 537 =
  34. 34.749 − 668 =
  35. 35.920 − 697 =
  36. 36.840 − 499 =
  37. 37.820 − 668 =
  38. 38.604 − 499 =
  39. 39.563 − 499 =
  40. 40.892 − 497 =

Answer key

  1. 136
  2. 299
  3. 371
  4. 226
  5. 255
  6. 161
  7. 175
  8. 419
  9. 681
  10. 794
  11. 68
  12. 560
  13. 55
  14. 19
  15. 116
  16. 78
  17. 520
  18. 165
  19. 83
  20. 339
  21. 148
  22. 37
  23. 142
  24. 592
  25. 20
  26. 686
  27. 402
  28. 17
  29. 425
  30. 116
  31. 456
  32. 159
  33. 129
  34. 81
  35. 223
  36. 341
  37. 152
  38. 105
  39. 64
  40. 395

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