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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 356 · 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. 1.889 − 498 =
  2. 2.917 − 798 =
  3. 3.414 − 208 =
  4. 4.986 − 678 =
  5. 5.766 − 627 =
  6. 6.391 − 309 =
  7. 7.756 − 398 =
  8. 8.445 − 137 =
  9. 9.316 − 199 =
  10. 10.709 − 508 =
  11. 11.680 − 568 =
  12. 12.846 − 197 =
  13. 13.836 − 799 =
  14. 14.848 − 797 =
  15. 15.836 − 798 =
  16. 16.627 − 599 =
  17. 17.816 − 557 =
  18. 18.605 − 398 =
  19. 19.970 − 298 =
  20. 20.413 − 289 =
  21. 21.786 − 299 =
  22. 22.907 − 247 =
  23. 23.594 − 489 =
  24. 24.824 − 398 =
  25. 25.558 − 407 =
  26. 26.798 − 559 =
  27. 27.402 − 298 =
  28. 28.981 − 497 =
  29. 29.616 − 119 =
  30. 30.888 − 397 =
  31. 31.945 − 797 =
  32. 32.374 − 247 =
  33. 33.320 − 238 =
  34. 34.415 − 297 =
  35. 35.251 − 117 =
  36. 36.695 − 369 =
  37. 37.353 − 197 =
  38. 38.924 − 267 =
  39. 39.539 − 458 =
  40. 40.737 − 679 =

Answer key

  1. 391
  2. 119
  3. 206
  4. 308
  5. 139
  6. 82
  7. 358
  8. 308
  9. 117
  10. 201
  11. 112
  12. 649
  13. 37
  14. 51
  15. 38
  16. 28
  17. 259
  18. 207
  19. 672
  20. 124
  21. 487
  22. 660
  23. 105
  24. 426
  25. 151
  26. 239
  27. 104
  28. 484
  29. 497
  30. 491
  31. 148
  32. 127
  33. 82
  34. 118
  35. 134
  36. 326
  37. 156
  38. 657
  39. 81
  40. 58

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