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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 623 · 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. 1.228 + 381 =
  2. 2.548 + 123 =
  3. 3.157 + 407 =
  4. 4.948 − 284 =
  5. 5.944 − 666 =
  6. 6.708 + 211 =
  7. 7.693 − 216 =
  8. 8.540 + 148 =
  9. 9.761 − 437 =
  10. 10.527 − 121 =
  11. 11.216 + 482 =
  12. 12.499 + 422 =
  13. 13.627 − 365 =
  14. 14.263 + 557 =
  15. 15.670 − 508 =
  16. 16.158 + 474 =
  17. 17.200 + 158 =
  18. 18.151 + 329 =
  19. 19.647 − 401 =
  20. 20.791 − 242 =
  21. 21.744 + 236 =
  22. 22.683 + 309 =
  23. 23.878 − 765 =
  24. 24.498 − 157 =
  25. 25.362 + 446 =
  26. 26.753 + 667 =
  27. 27.628 + 449 =
  28. 28.124 + 149 =
  29. 29.291 + 588 =
  30. 30.381 + 532 =
  31. 31.588 + 248 =
  32. 32.176 + 492 =
  33. 33.293 + 121 =
  34. 34.679 − 319 =
  35. 35.302 + 175 =
  36. 36.615 − 439 =
  37. 37.665 − 201 =
  38. 38.672 − 386 =
  39. 39.727 − 455 =
  40. 40.622 − 263 =

Answer key

  1. 609
  2. 671
  3. 564
  4. 664
  5. 278
  6. 919
  7. 477
  8. 688
  9. 324
  10. 406
  11. 698
  12. 921
  13. 262
  14. 820
  15. 162
  16. 632
  17. 358
  18. 480
  19. 246
  20. 549
  21. 980
  22. 992
  23. 113
  24. 341
  25. 808
  26. 1420
  27. 1077
  28. 273
  29. 879
  30. 913
  31. 836
  32. 668
  33. 414
  34. 360
  35. 477
  36. 176
  37. 464
  38. 286
  39. 272
  40. 359

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