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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 884 · 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. 1.573 − 469 =
  2. 2.761 − 129 =
  3. 3.550 − 398 =
  4. 4.736 − 519 =
  5. 5.972 − 637 =
  6. 6.832 − 799 =
  7. 7.512 − 497 =
  8. 8.858 − 198 =
  9. 9.238 − 168 =
  10. 10.934 − 559 =
  11. 11.529 − 298 =
  12. 12.685 − 298 =
  13. 13.306 − 169 =
  14. 14.730 − 178 =
  15. 15.669 − 207 =
  16. 16.344 − 197 =
  17. 17.484 − 299 =
  18. 18.929 − 399 =
  19. 19.837 − 599 =
  20. 20.943 − 798 =
  21. 21.589 − 149 =
  22. 22.753 − 697 =
  23. 23.571 − 398 =
  24. 24.340 − 297 =
  25. 25.639 − 498 =
  26. 26.991 − 298 =
  27. 27.399 − 188 =
  28. 28.862 − 449 =
  29. 29.992 − 319 =
  30. 30.977 − 798 =
  31. 31.873 − 597 =
  32. 32.685 − 598 =
  33. 33.740 − 599 =
  34. 34.887 − 599 =
  35. 35.580 − 559 =
  36. 36.722 − 637 =
  37. 37.899 − 699 =
  38. 38.962 − 397 =
  39. 39.521 − 298 =
  40. 40.983 − 239 =

Answer key

  1. 104
  2. 632
  3. 152
  4. 217
  5. 335
  6. 33
  7. 15
  8. 660
  9. 70
  10. 375
  11. 231
  12. 387
  13. 137
  14. 552
  15. 462
  16. 147
  17. 185
  18. 530
  19. 238
  20. 145
  21. 440
  22. 56
  23. 173
  24. 43
  25. 141
  26. 693
  27. 211
  28. 413
  29. 673
  30. 179
  31. 276
  32. 87
  33. 141
  34. 288
  35. 21
  36. 85
  37. 200
  38. 565
  39. 223
  40. 744

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