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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 462 · 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. 1.921 − 798 =
  2. 2.507 − 249 =
  3. 3.706 − 648 =
  4. 4.882 − 498 =
  5. 5.922 − 297 =
  6. 6.895 − 197 =
  7. 7.668 − 299 =
  8. 8.738 − 597 =
  9. 9.959 − 798 =
  10. 10.623 − 598 =
  11. 11.433 − 237 =
  12. 12.695 − 119 =
  13. 13.910 − 798 =
  14. 14.968 − 797 =
  15. 15.898 − 599 =
  16. 16.311 − 137 =
  17. 17.748 − 407 =
  18. 18.451 − 198 =
  19. 19.822 − 699 =
  20. 20.487 − 368 =
  21. 21.720 − 297 =
  22. 22.457 − 297 =
  23. 23.790 − 299 =
  24. 24.999 − 189 =
  25. 25.997 − 368 =
  26. 26.603 − 199 =
  27. 27.437 − 277 =
  28. 28.766 − 399 =
  29. 29.539 − 298 =
  30. 30.372 − 159 =
  31. 31.844 − 687 =
  32. 32.679 − 197 =
  33. 33.445 − 198 =
  34. 34.670 − 138 =
  35. 35.891 − 697 =
  36. 36.337 − 297 =
  37. 37.816 − 799 =
  38. 38.874 − 398 =
  39. 39.844 − 299 =
  40. 40.868 − 599 =

Answer key

  1. 123
  2. 258
  3. 58
  4. 384
  5. 625
  6. 698
  7. 369
  8. 141
  9. 161
  10. 25
  11. 196
  12. 576
  13. 112
  14. 171
  15. 299
  16. 174
  17. 341
  18. 253
  19. 123
  20. 119
  21. 423
  22. 160
  23. 491
  24. 810
  25. 629
  26. 404
  27. 160
  28. 367
  29. 241
  30. 213
  31. 157
  32. 482
  33. 247
  34. 532
  35. 194
  36. 40
  37. 17
  38. 476
  39. 545
  40. 269

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