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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 580 · 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. 1.833 − 588 =
  2. 2.546 − 399 =
  3. 3.880 − 559 =
  4. 4.563 − 387 =
  5. 5.600 − 497 =
  6. 6.941 − 177 =
  7. 7.714 − 699 =
  8. 8.983 − 697 =
  9. 9.776 − 697 =
  10. 10.684 − 588 =
  11. 11.874 − 507 =
  12. 12.448 − 189 =
  13. 13.814 − 599 =
  14. 14.886 − 427 =
  15. 15.435 − 387 =
  16. 16.678 − 257 =
  17. 17.310 − 257 =
  18. 18.582 − 429 =
  19. 19.809 − 378 =
  20. 20.725 − 299 =
  21. 21.636 − 517 =
  22. 22.764 − 289 =
  23. 23.629 − 398 =
  24. 24.295 − 198 =
  25. 25.698 − 358 =
  26. 26.754 − 699 =
  27. 27.974 − 527 =
  28. 28.768 − 399 =
  29. 29.816 − 348 =
  30. 30.726 − 399 =
  31. 31.967 − 258 =
  32. 32.953 − 797 =
  33. 33.834 − 798 =
  34. 34.753 − 698 =
  35. 35.886 − 698 =
  36. 36.982 − 247 =
  37. 37.590 − 148 =
  38. 38.821 − 697 =
  39. 39.316 − 299 =
  40. 40.477 − 297 =

Answer key

  1. 245
  2. 147
  3. 321
  4. 176
  5. 103
  6. 764
  7. 15
  8. 286
  9. 79
  10. 96
  11. 367
  12. 259
  13. 215
  14. 459
  15. 48
  16. 421
  17. 53
  18. 153
  19. 431
  20. 426
  21. 119
  22. 475
  23. 231
  24. 97
  25. 340
  26. 55
  27. 447
  28. 369
  29. 468
  30. 327
  31. 709
  32. 156
  33. 36
  34. 55
  35. 188
  36. 735
  37. 442
  38. 124
  39. 17
  40. 180

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