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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 397 · 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. 1.869 − 736 =
  2. 2.243 + 341 =
  3. 3.315 + 478 =
  4. 4.454 − 178 =
  5. 5.253 + 242 =
  6. 6.724 − 291 =
  7. 7.486 + 338 =
  8. 8.516 − 161 =
  9. 9.768 + 246 =
  10. 10.881 − 581 =
  11. 11.757 − 527 =
  12. 12.464 − 213 =
  13. 13.482 − 127 =
  14. 14.134 + 511 =
  15. 15.894 − 477 =
  16. 16.593 − 422 =
  17. 17.347 + 391 =
  18. 18.530 − 271 =
  19. 19.469 + 191 =
  20. 20.873 − 365 =
  21. 21.159 + 201 =
  22. 22.247 + 608 =
  23. 23.289 + 536 =
  24. 24.582 + 326 =
  25. 25.713 + 538 =
  26. 26.380 + 553 =
  27. 27.965 − 475 =
  28. 28.806 − 313 =
  29. 29.849 − 664 =
  30. 30.717 + 216 =
  31. 31.296 + 255 =
  32. 32.753 + 223 =
  33. 33.411 + 201 =
  34. 34.370 + 684 =
  35. 35.398 + 687 =
  36. 36.217 + 588 =
  37. 37.463 + 496 =
  38. 38.712 − 515 =
  39. 39.538 + 123 =
  40. 40.826 − 352 =

Answer key

  1. 133
  2. 584
  3. 793
  4. 276
  5. 495
  6. 433
  7. 824
  8. 355
  9. 1014
  10. 300
  11. 230
  12. 251
  13. 355
  14. 645
  15. 417
  16. 171
  17. 738
  18. 259
  19. 660
  20. 508
  21. 360
  22. 855
  23. 825
  24. 908
  25. 1251
  26. 933
  27. 490
  28. 493
  29. 185
  30. 933
  31. 551
  32. 976
  33. 612
  34. 1054
  35. 1085
  36. 805
  37. 959
  38. 197
  39. 661
  40. 474

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