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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 377 · 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. 1.128 + 248 =
  2. 2.539 − 344 =
  3. 3.436 − 185 =
  4. 4.620 − 477 =
  5. 5.709 + 261 =
  6. 6.127 + 664 =
  7. 7.761 + 603 =
  8. 8.895 − 773 =
  9. 9.746 − 623 =
  10. 10.744 + 477 =
  11. 11.309 + 112 =
  12. 12.324 + 464 =
  13. 13.164 + 123 =
  14. 14.654 + 123 =
  15. 15.452 + 611 =
  16. 16.684 − 498 =
  17. 17.788 + 553 =
  18. 18.697 − 521 =
  19. 19.549 − 392 =
  20. 20.283 + 245 =
  21. 21.170 + 431 =
  22. 22.682 + 646 =
  23. 23.491 − 189 =
  24. 24.633 + 548 =
  25. 25.655 − 449 =
  26. 26.800 − 612 =
  27. 27.555 + 564 =
  28. 28.771 + 491 =
  29. 29.751 + 197 =
  30. 30.664 + 242 =
  31. 31.813 − 521 =
  32. 32.678 + 408 =
  33. 33.806 − 687 =
  34. 34.778 + 655 =
  35. 35.469 + 442 =
  36. 36.521 − 126 =
  37. 37.556 + 532 =
  38. 38.821 − 162 =
  39. 39.825 − 489 =
  40. 40.407 + 397 =

Answer key

  1. 376
  2. 195
  3. 251
  4. 143
  5. 970
  6. 791
  7. 1364
  8. 122
  9. 123
  10. 1221
  11. 421
  12. 788
  13. 287
  14. 777
  15. 1063
  16. 186
  17. 1341
  18. 176
  19. 157
  20. 528
  21. 601
  22. 1328
  23. 302
  24. 1181
  25. 206
  26. 188
  27. 1119
  28. 1262
  29. 948
  30. 906
  31. 292
  32. 1086
  33. 119
  34. 1433
  35. 911
  36. 395
  37. 1088
  38. 659
  39. 336
  40. 804

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