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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 274 · 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. 1.453 + 344 =
  2. 2.700 + 453 =
  3. 3.741 + 204 =
  4. 4.524 − 416 =
  5. 5.841 − 326 =
  6. 6.443 + 156 =
  7. 7.424 − 281 =
  8. 8.390 + 554 =
  9. 9.490 − 207 =
  10. 10.462 + 635 =
  11. 11.217 + 308 =
  12. 12.567 + 514 =
  13. 13.455 − 129 =
  14. 14.498 − 219 =
  15. 15.517 − 392 =
  16. 16.636 + 668 =
  17. 17.418 − 131 =
  18. 18.675 + 185 =
  19. 19.515 − 255 =
  20. 20.651 + 621 =
  21. 21.591 + 454 =
  22. 22.758 + 675 =
  23. 23.672 + 502 =
  24. 24.441 + 524 =
  25. 25.582 − 361 =
  26. 26.594 − 436 =
  27. 27.927 − 351 =
  28. 28.529 − 314 =
  29. 29.473 + 415 =
  30. 30.544 − 248 =
  31. 31.685 + 605 =
  32. 32.669 + 363 =
  33. 33.255 + 186 =
  34. 34.785 + 565 =
  35. 35.527 − 181 =
  36. 36.464 − 165 =
  37. 37.294 + 507 =
  38. 38.658 − 253 =
  39. 39.580 − 146 =
  40. 40.637 + 368 =

Answer key

  1. 797
  2. 1153
  3. 945
  4. 108
  5. 515
  6. 599
  7. 143
  8. 944
  9. 283
  10. 1097
  11. 525
  12. 1081
  13. 326
  14. 279
  15. 125
  16. 1304
  17. 287
  18. 860
  19. 260
  20. 1272
  21. 1045
  22. 1433
  23. 1174
  24. 965
  25. 221
  26. 158
  27. 576
  28. 215
  29. 888
  30. 296
  31. 1290
  32. 1032
  33. 441
  34. 1350
  35. 346
  36. 299
  37. 801
  38. 405
  39. 434
  40. 1005

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