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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 307 · 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. 1.864 − 599 =
  2. 2.813 − 698 =
  3. 3.830 − 798 =
  4. 4.818 − 699 =
  5. 5.698 − 417 =
  6. 6.884 − 158 =
  7. 7.940 − 699 =
  8. 8.683 − 369 =
  9. 9.541 − 347 =
  10. 10.195 − 167 =
  11. 11.712 − 697 =
  12. 12.889 − 637 =
  13. 13.857 − 527 =
  14. 14.844 − 398 =
  15. 15.514 − 498 =
  16. 16.928 − 197 =
  17. 17.563 − 449 =
  18. 18.426 − 287 =
  19. 19.600 − 157 =
  20. 20.856 − 698 =
  21. 21.645 − 208 =
  22. 22.552 − 237 =
  23. 23.871 − 199 =
  24. 24.536 − 397 =
  25. 25.711 − 599 =
  26. 26.563 − 497 =
  27. 27.701 − 518 =
  28. 28.608 − 548 =
  29. 29.895 − 198 =
  30. 30.770 − 429 =
  31. 31.542 − 138 =
  32. 32.905 − 798 =
  33. 33.650 − 199 =
  34. 34.865 − 797 =
  35. 35.952 − 649 =
  36. 36.529 − 148 =
  37. 37.843 − 797 =
  38. 38.925 − 597 =
  39. 39.881 − 207 =
  40. 40.606 − 467 =

Answer key

  1. 265
  2. 115
  3. 32
  4. 119
  5. 281
  6. 726
  7. 241
  8. 314
  9. 194
  10. 28
  11. 15
  12. 252
  13. 330
  14. 446
  15. 16
  16. 731
  17. 114
  18. 139
  19. 443
  20. 158
  21. 437
  22. 315
  23. 672
  24. 139
  25. 112
  26. 66
  27. 183
  28. 60
  29. 697
  30. 341
  31. 404
  32. 107
  33. 451
  34. 68
  35. 303
  36. 381
  37. 46
  38. 328
  39. 674
  40. 139

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