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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 777 · 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. 1.506 − 319 =
  2. 2.569 − 218 =
  3. 3.391 − 297 =
  4. 4.752 − 319 =
  5. 5.967 − 499 =
  6. 6.776 − 697 =
  7. 7.996 − 128 =
  8. 8.881 − 198 =
  9. 9.602 − 298 =
  10. 10.585 − 497 =
  11. 11.698 − 368 =
  12. 12.365 − 298 =
  13. 13.552 − 199 =
  14. 14.887 − 698 =
  15. 15.762 − 299 =
  16. 16.329 − 148 =
  17. 17.861 − 117 =
  18. 18.335 − 257 =
  19. 19.542 − 397 =
  20. 20.928 − 628 =
  21. 21.816 − 498 =
  22. 22.754 − 157 =
  23. 23.818 − 538 =
  24. 24.865 − 798 =
  25. 25.722 − 699 =
  26. 26.443 − 279 =
  27. 27.351 − 218 =
  28. 28.343 − 297 =
  29. 29.438 − 199 =
  30. 30.742 − 499 =
  31. 31.360 − 299 =
  32. 32.385 − 197 =
  33. 33.713 − 529 =
  34. 34.698 − 567 =
  35. 35.312 − 197 =
  36. 36.827 − 197 =
  37. 37.957 − 187 =
  38. 38.363 − 297 =
  39. 39.951 − 499 =
  40. 40.496 − 407 =

Answer key

  1. 187
  2. 351
  3. 94
  4. 433
  5. 468
  6. 79
  7. 868
  8. 683
  9. 304
  10. 88
  11. 330
  12. 67
  13. 353
  14. 189
  15. 463
  16. 181
  17. 744
  18. 78
  19. 145
  20. 300
  21. 318
  22. 597
  23. 280
  24. 67
  25. 23
  26. 164
  27. 133
  28. 46
  29. 239
  30. 243
  31. 61
  32. 188
  33. 184
  34. 131
  35. 115
  36. 630
  37. 770
  38. 66
  39. 452
  40. 89

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