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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 92 · 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. 1.821 − 199 =
  2. 2.586 − 398 =
  3. 3.878 − 537 =
  4. 4.324 − 119 =
  5. 5.639 − 617 =
  6. 6.847 − 669 =
  7. 7.800 − 479 =
  8. 8.612 − 498 =
  9. 9.637 − 497 =
  10. 10.766 − 697 =
  11. 11.991 − 239 =
  12. 12.887 − 179 =
  13. 13.971 − 597 =
  14. 14.812 − 799 =
  15. 15.472 − 298 =
  16. 16.831 − 798 =
  17. 17.254 − 149 =
  18. 18.278 − 197 =
  19. 19.585 − 388 =
  20. 20.484 − 297 =
  21. 21.330 − 258 =
  22. 22.949 − 449 =
  23. 23.720 − 497 =
  24. 24.954 − 797 =
  25. 25.637 − 599 =
  26. 26.244 − 149 =
  27. 27.845 − 369 =
  28. 28.970 − 798 =
  29. 29.727 − 297 =
  30. 30.897 − 687 =
  31. 31.951 − 799 =
  32. 32.955 − 289 =
  33. 33.822 − 698 =
  34. 34.777 − 539 =
  35. 35.303 − 229 =
  36. 36.818 − 698 =
  37. 37.765 − 659 =
  38. 38.534 − 299 =
  39. 39.944 − 297 =
  40. 40.652 − 558 =

Answer key

  1. 622
  2. 188
  3. 341
  4. 205
  5. 22
  6. 178
  7. 321
  8. 114
  9. 140
  10. 69
  11. 752
  12. 708
  13. 374
  14. 13
  15. 174
  16. 33
  17. 105
  18. 81
  19. 197
  20. 187
  21. 72
  22. 500
  23. 223
  24. 157
  25. 38
  26. 95
  27. 476
  28. 172
  29. 430
  30. 210
  31. 152
  32. 666
  33. 124
  34. 238
  35. 74
  36. 120
  37. 106
  38. 235
  39. 647
  40. 94

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