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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 685 · 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. 1.427 + 139 =
  2. 2.554 − 171 =
  3. 3.238 + 203 =
  4. 4.562 − 221 =
  5. 5.880 − 461 =
  6. 6.982 − 252 =
  7. 7.383 + 345 =
  8. 8.485 − 232 =
  9. 9.687 − 288 =
  10. 10.782 + 337 =
  11. 11.540 − 438 =
  12. 12.881 − 375 =
  13. 13.984 − 592 =
  14. 14.500 + 531 =
  15. 15.936 − 823 =
  16. 16.303 + 522 =
  17. 17.303 + 141 =
  18. 18.968 − 729 =
  19. 19.542 + 447 =
  20. 20.475 − 151 =
  21. 21.300 + 271 =
  22. 22.665 + 391 =
  23. 23.608 − 319 =
  24. 24.413 + 309 =
  25. 25.197 + 454 =
  26. 26.667 + 372 =
  27. 27.592 − 425 =
  28. 28.293 + 285 =
  29. 29.647 + 271 =
  30. 30.171 + 351 =
  31. 31.448 − 129 =
  32. 32.842 − 741 =
  33. 33.329 + 161 =
  34. 34.232 + 285 =
  35. 35.291 + 188 =
  36. 36.199 + 529 =
  37. 37.965 − 126 =
  38. 38.332 + 626 =
  39. 39.927 − 336 =
  40. 40.687 + 673 =

Answer key

  1. 566
  2. 383
  3. 441
  4. 341
  5. 419
  6. 730
  7. 728
  8. 253
  9. 399
  10. 1119
  11. 102
  12. 506
  13. 392
  14. 1031
  15. 113
  16. 825
  17. 444
  18. 239
  19. 989
  20. 324
  21. 571
  22. 1056
  23. 289
  24. 722
  25. 651
  26. 1039
  27. 167
  28. 578
  29. 918
  30. 522
  31. 319
  32. 101
  33. 490
  34. 517
  35. 479
  36. 728
  37. 839
  38. 958
  39. 591
  40. 1360

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