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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 989 · 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. 1.542 + 379 =
  2. 2.295 + 531 =
  3. 3.183 + 422 =
  4. 4.724 − 607 =
  5. 5.463 − 112 =
  6. 6.538 − 156 =
  7. 7.369 + 187 =
  8. 8.438 + 143 =
  9. 9.940 − 801 =
  10. 10.343 + 245 =
  11. 11.472 + 399 =
  12. 12.143 + 372 =
  13. 13.209 + 682 =
  14. 14.668 + 531 =
  15. 15.778 + 457 =
  16. 16.289 + 434 =
  17. 17.513 + 677 =
  18. 18.167 + 308 =
  19. 19.785 + 355 =
  20. 20.983 − 472 =
  21. 21.535 − 134 =
  22. 22.480 − 286 =
  23. 23.930 − 333 =
  24. 24.443 + 256 =
  25. 25.743 + 598 =
  26. 26.286 + 478 =
  27. 27.214 + 574 =
  28. 28.491 + 471 =
  29. 29.336 + 505 =
  30. 30.159 + 398 =
  31. 31.137 + 338 =
  32. 32.666 − 395 =
  33. 33.139 + 274 =
  34. 34.647 − 308 =
  35. 35.729 + 125 =
  36. 36.302 + 635 =
  37. 37.278 + 311 =
  38. 38.480 − 337 =
  39. 39.381 + 387 =
  40. 40.628 + 631 =

Answer key

  1. 921
  2. 826
  3. 605
  4. 117
  5. 351
  6. 382
  7. 556
  8. 581
  9. 139
  10. 588
  11. 871
  12. 515
  13. 891
  14. 1199
  15. 1235
  16. 723
  17. 1190
  18. 475
  19. 1140
  20. 511
  21. 401
  22. 194
  23. 597
  24. 699
  25. 1341
  26. 764
  27. 788
  28. 962
  29. 841
  30. 557
  31. 475
  32. 271
  33. 413
  34. 339
  35. 854
  36. 937
  37. 589
  38. 143
  39. 768
  40. 1259

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