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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 630 · 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. 1.728 + 394 =
  2. 2.556 + 611 =
  3. 3.784 + 352 =
  4. 4.297 + 543 =
  5. 5.756 − 597 =
  6. 6.453 + 477 =
  7. 7.336 + 383 =
  8. 8.541 + 184 =
  9. 9.411 + 535 =
  10. 10.328 + 409 =
  11. 11.619 − 391 =
  12. 12.124 + 281 =
  13. 13.576 − 363 =
  14. 14.706 + 165 =
  15. 15.264 + 666 =
  16. 16.710 + 278 =
  17. 17.815 − 505 =
  18. 18.367 + 146 =
  19. 19.314 + 429 =
  20. 20.707 + 521 =
  21. 21.285 + 607 =
  22. 22.365 + 445 =
  23. 23.441 − 312 =
  24. 24.564 − 194 =
  25. 25.847 − 629 =
  26. 26.364 + 274 =
  27. 27.810 − 561 =
  28. 28.466 − 317 =
  29. 29.405 + 561 =
  30. 30.451 + 424 =
  31. 31.595 − 207 =
  32. 32.929 − 365 =
  33. 33.423 + 545 =
  34. 34.429 − 289 =
  35. 35.418 + 514 =
  36. 36.735 + 461 =
  37. 37.469 − 305 =
  38. 38.230 + 448 =
  39. 39.548 − 376 =
  40. 40.196 + 602 =

Answer key

  1. 1122
  2. 1167
  3. 1136
  4. 840
  5. 159
  6. 930
  7. 719
  8. 725
  9. 946
  10. 737
  11. 228
  12. 405
  13. 213
  14. 871
  15. 930
  16. 988
  17. 310
  18. 513
  19. 743
  20. 1228
  21. 892
  22. 810
  23. 129
  24. 370
  25. 218
  26. 638
  27. 249
  28. 149
  29. 966
  30. 875
  31. 388
  32. 564
  33. 968
  34. 140
  35. 932
  36. 1196
  37. 164
  38. 678
  39. 172
  40. 798

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