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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 304 · 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. 1.757 − 539 =
  2. 2.751 − 257 =
  3. 3.319 − 297 =
  4. 4.848 − 199 =
  5. 5.331 − 248 =
  6. 6.412 − 199 =
  7. 7.916 − 197 =
  8. 8.545 − 468 =
  9. 9.946 − 798 =
  10. 10.754 − 497 =
  11. 11.697 − 509 =
  12. 12.777 − 698 =
  13. 13.640 − 429 =
  14. 14.883 − 698 =
  15. 15.743 − 159 =
  16. 16.577 − 498 =
  17. 17.810 − 287 =
  18. 18.553 − 517 =
  19. 19.160 − 127 =
  20. 20.870 − 417 =
  21. 21.241 − 198 =
  22. 22.672 − 599 =
  23. 23.255 − 198 =
  24. 24.662 − 558 =
  25. 25.550 − 229 =
  26. 26.742 − 177 =
  27. 27.534 − 187 =
  28. 28.807 − 298 =
  29. 29.500 − 399 =
  30. 30.898 − 608 =
  31. 31.637 − 398 =
  32. 32.853 − 797 =
  33. 33.980 − 799 =
  34. 34.849 − 697 =
  35. 35.869 − 529 =
  36. 36.834 − 697 =
  37. 37.827 − 797 =
  38. 38.826 − 797 =
  39. 39.972 − 369 =
  40. 40.884 − 498 =

Answer key

  1. 218
  2. 494
  3. 22
  4. 649
  5. 83
  6. 213
  7. 719
  8. 77
  9. 148
  10. 257
  11. 188
  12. 79
  13. 211
  14. 185
  15. 584
  16. 79
  17. 523
  18. 36
  19. 33
  20. 453
  21. 43
  22. 73
  23. 57
  24. 104
  25. 321
  26. 565
  27. 347
  28. 509
  29. 101
  30. 290
  31. 239
  32. 56
  33. 181
  34. 152
  35. 340
  36. 137
  37. 30
  38. 29
  39. 603
  40. 386

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