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3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 270 · 40 questions
TalentJR

How to do it in your head (Hundreds first): Keep the first number as it is and split the second into hundreds, tens and ones. Add (or take away) the hundreds first, then the tens. Finish with the ones — bridge through a ten if you need to.

NameDateTime takenScore ___ / 40
  1. 1.702 + 585 =
  2. 2.446 − 155 =
  3. 3.741 + 231 =
  4. 4.612 + 666 =
  5. 5.469 + 351 =
  6. 6.247 + 673 =
  7. 7.857 − 221 =
  8. 8.501 − 221 =
  9. 9.440 + 621 =
  10. 10.923 − 326 =
  11. 11.574 − 204 =
  12. 12.304 + 131 =
  13. 13.787 − 251 =
  14. 14.586 + 622 =
  15. 15.972 − 579 =
  16. 16.797 − 161 =
  17. 17.636 − 311 =
  18. 18.156 + 661 =
  19. 19.306 + 436 =
  20. 20.390 + 252 =
  21. 21.759 − 397 =
  22. 22.503 − 173 =
  23. 23.576 − 143 =
  24. 24.317 + 645 =
  25. 25.778 − 392 =
  26. 26.862 − 351 =
  27. 27.834 − 255 =
  28. 28.260 + 613 =
  29. 29.638 − 409 =
  30. 30.523 + 472 =
  31. 31.589 − 355 =
  32. 32.860 − 371 =
  33. 33.779 − 409 =
  34. 34.596 − 188 =
  35. 35.686 + 368 =
  36. 36.659 + 527 =
  37. 37.776 + 458 =
  38. 38.318 + 629 =
  39. 39.773 − 405 =
  40. 40.640 + 471 =

Answer key

  1. 1287
  2. 291
  3. 972
  4. 1278
  5. 820
  6. 920
  7. 636
  8. 280
  9. 1061
  10. 597
  11. 370
  12. 435
  13. 536
  14. 1208
  15. 393
  16. 636
  17. 325
  18. 817
  19. 742
  20. 642
  21. 362
  22. 330
  23. 433
  24. 962
  25. 386
  26. 511
  27. 579
  28. 873
  29. 229
  30. 995
  31. 234
  32. 489
  33. 370
  34. 408
  35. 1054
  36. 1186
  37. 1234
  38. 947
  39. 368
  40. 1111

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