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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 253 · 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. 1.910 − 798 =
  2. 2.722 − 599 =
  3. 3.661 − 489 =
  4. 4.644 − 567 =
  5. 5.595 − 497 =
  6. 6.951 − 797 =
  7. 7.803 − 697 =
  8. 8.861 − 519 =
  9. 9.635 − 598 =
  10. 10.772 − 699 =
  11. 11.642 − 627 =
  12. 12.952 − 797 =
  13. 13.784 − 689 =
  14. 14.487 − 279 =
  15. 15.854 − 797 =
  16. 16.561 − 119 =
  17. 17.831 − 588 =
  18. 18.433 − 369 =
  19. 19.698 − 328 =
  20. 20.801 − 138 =
  21. 21.629 − 579 =
  22. 22.818 − 137 =
  23. 23.620 − 127 =
  24. 24.423 − 198 =
  25. 25.605 − 439 =
  26. 26.278 − 197 =
  27. 27.175 − 137 =
  28. 28.846 − 689 =
  29. 29.328 − 247 =
  30. 30.894 − 598 =
  31. 31.723 − 397 =
  32. 32.386 − 229 =
  33. 33.881 − 697 =
  34. 34.566 − 298 =
  35. 35.731 − 518 =
  36. 36.968 − 399 =
  37. 37.908 − 797 =
  38. 38.738 − 399 =
  39. 39.686 − 648 =
  40. 40.655 − 298 =

Answer key

  1. 112
  2. 123
  3. 172
  4. 77
  5. 98
  6. 154
  7. 106
  8. 342
  9. 37
  10. 73
  11. 15
  12. 155
  13. 95
  14. 208
  15. 57
  16. 442
  17. 243
  18. 64
  19. 370
  20. 663
  21. 50
  22. 681
  23. 493
  24. 225
  25. 166
  26. 81
  27. 38
  28. 157
  29. 81
  30. 296
  31. 326
  32. 157
  33. 184
  34. 268
  35. 213
  36. 569
  37. 111
  38. 339
  39. 38
  40. 357

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