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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 983 · 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. 1.636 − 597 =
  2. 2.333 − 247 =
  3. 3.444 − 407 =
  4. 4.994 − 638 =
  5. 5.828 − 597 =
  6. 6.802 − 389 =
  7. 7.949 − 698 =
  8. 8.885 − 799 =
  9. 9.720 − 638 =
  10. 10.984 − 197 =
  11. 11.924 − 299 =
  12. 12.738 − 469 =
  13. 13.332 − 269 =
  14. 14.663 − 297 =
  15. 15.226 − 187 =
  16. 16.490 − 308 =
  17. 17.745 − 597 =
  18. 18.731 − 497 =
  19. 19.899 − 697 =
  20. 20.831 − 367 =
  21. 21.733 − 408 =
  22. 22.852 − 798 =
  23. 23.973 − 297 =
  24. 24.683 − 227 =
  25. 25.853 − 799 =
  26. 26.821 − 799 =
  27. 27.928 − 799 =
  28. 28.553 − 497 =
  29. 29.971 − 599 =
  30. 30.811 − 377 =
  31. 31.923 − 599 =
  32. 32.505 − 257 =
  33. 33.914 − 209 =
  34. 34.915 − 698 =
  35. 35.933 − 577 =
  36. 36.598 − 498 =
  37. 37.892 − 629 =
  38. 38.949 − 669 =
  39. 39.772 − 689 =
  40. 40.678 − 619 =

Answer key

  1. 39
  2. 86
  3. 37
  4. 356
  5. 231
  6. 413
  7. 251
  8. 86
  9. 82
  10. 787
  11. 625
  12. 269
  13. 63
  14. 366
  15. 39
  16. 182
  17. 148
  18. 234
  19. 202
  20. 464
  21. 325
  22. 54
  23. 676
  24. 456
  25. 54
  26. 22
  27. 129
  28. 56
  29. 372
  30. 434
  31. 324
  32. 248
  33. 705
  34. 217
  35. 356
  36. 100
  37. 263
  38. 280
  39. 83
  40. 59

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