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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 644 · 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. 1.642 + 621 =
  2. 2.856 − 352 =
  3. 3.815 − 321 =
  4. 4.578 + 177 =
  5. 5.416 + 121 =
  6. 6.322 + 434 =
  7. 7.234 + 581 =
  8. 8.319 + 339 =
  9. 9.472 − 135 =
  10. 10.752 − 244 =
  11. 11.401 + 483 =
  12. 12.562 − 145 =
  13. 13.479 + 424 =
  14. 14.788 + 216 =
  15. 15.842 − 559 =
  16. 16.197 + 181 =
  17. 17.484 − 208 =
  18. 18.438 + 257 =
  19. 19.684 − 123 =
  20. 20.437 + 477 =
  21. 21.517 − 232 =
  22. 22.907 − 593 =
  23. 23.598 − 349 =
  24. 24.236 + 428 =
  25. 25.973 − 445 =
  26. 26.517 + 237 =
  27. 27.457 − 224 =
  28. 28.720 − 155 =
  29. 29.157 + 224 =
  30. 30.526 − 271 =
  31. 31.664 − 511 =
  32. 32.431 − 233 =
  33. 33.642 + 517 =
  34. 34.516 − 362 =
  35. 35.767 + 332 =
  36. 36.146 + 193 =
  37. 37.643 − 145 =
  38. 38.567 + 477 =
  39. 39.694 + 146 =
  40. 40.630 + 167 =

Answer key

  1. 1263
  2. 504
  3. 494
  4. 755
  5. 537
  6. 756
  7. 815
  8. 658
  9. 337
  10. 508
  11. 884
  12. 417
  13. 903
  14. 1004
  15. 283
  16. 378
  17. 276
  18. 695
  19. 561
  20. 914
  21. 285
  22. 314
  23. 249
  24. 664
  25. 528
  26. 754
  27. 233
  28. 565
  29. 381
  30. 255
  31. 153
  32. 198
  33. 1159
  34. 154
  35. 1099
  36. 339
  37. 498
  38. 1044
  39. 840
  40. 797

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