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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 729 · 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. 1.445 − 129 =
  2. 2.156 + 171 =
  3. 3.194 + 161 =
  4. 4.308 + 412 =
  5. 5.623 + 448 =
  6. 6.398 + 371 =
  7. 7.165 + 246 =
  8. 8.568 − 379 =
  9. 9.179 + 363 =
  10. 10.714 + 644 =
  11. 11.702 + 132 =
  12. 12.529 + 341 =
  13. 13.341 + 595 =
  14. 14.856 − 294 =
  15. 15.785 + 352 =
  16. 16.426 − 263 =
  17. 17.181 + 576 =
  18. 18.519 + 648 =
  19. 19.336 + 147 =
  20. 20.775 − 392 =
  21. 21.180 + 614 =
  22. 22.663 + 208 =
  23. 23.492 − 295 =
  24. 24.666 − 524 =
  25. 25.395 + 171 =
  26. 26.641 − 443 =
  27. 27.754 − 319 =
  28. 28.751 + 445 =
  29. 29.397 + 287 =
  30. 30.540 − 364 =
  31. 31.142 + 145 =
  32. 32.417 − 236 =
  33. 33.617 − 252 =
  34. 34.384 + 353 =
  35. 35.203 + 596 =
  36. 36.597 + 285 =
  37. 37.453 + 229 =
  38. 38.868 − 434 =
  39. 39.845 − 221 =
  40. 40.660 + 436 =

Answer key

  1. 316
  2. 327
  3. 355
  4. 720
  5. 1071
  6. 769
  7. 411
  8. 189
  9. 542
  10. 1358
  11. 834
  12. 870
  13. 936
  14. 562
  15. 1137
  16. 163
  17. 757
  18. 1167
  19. 483
  20. 383
  21. 794
  22. 871
  23. 197
  24. 142
  25. 566
  26. 198
  27. 435
  28. 1196
  29. 684
  30. 176
  31. 287
  32. 181
  33. 365
  34. 737
  35. 799
  36. 882
  37. 682
  38. 434
  39. 624
  40. 1096

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