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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 747 · 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. 1.488 + 171 =
  2. 2.426 − 171 =
  3. 3.238 + 368 =
  4. 4.451 − 171 =
  5. 5.861 − 352 =
  6. 6.574 − 423 =
  7. 7.561 + 506 =
  8. 8.745 + 151 =
  9. 9.446 − 203 =
  10. 10.522 − 375 =
  11. 11.754 + 587 =
  12. 12.548 − 172 =
  13. 13.695 − 531 =
  14. 14.325 + 191 =
  15. 15.606 + 259 =
  16. 16.222 + 169 =
  17. 17.311 + 401 =
  18. 18.540 − 151 =
  19. 19.498 + 244 =
  20. 20.449 − 212 =
  21. 21.896 − 792 =
  22. 22.552 − 137 =
  23. 23.233 + 397 =
  24. 24.461 + 655 =
  25. 25.519 + 146 =
  26. 26.427 − 196 =
  27. 27.373 + 389 =
  28. 28.275 + 478 =
  29. 29.455 − 221 =
  30. 30.663 − 486 =
  31. 31.782 + 567 =
  32. 32.534 + 387 =
  33. 33.418 + 122 =
  34. 34.369 + 514 =
  35. 35.466 + 689 =
  36. 36.472 − 114 =
  37. 37.576 − 183 =
  38. 38.348 + 665 =
  39. 39.432 − 309 =
  40. 40.602 − 114 =

Answer key

  1. 659
  2. 255
  3. 606
  4. 280
  5. 509
  6. 151
  7. 1067
  8. 896
  9. 243
  10. 147
  11. 1341
  12. 376
  13. 164
  14. 516
  15. 865
  16. 391
  17. 712
  18. 389
  19. 742
  20. 237
  21. 104
  22. 415
  23. 630
  24. 1116
  25. 665
  26. 231
  27. 762
  28. 753
  29. 234
  30. 177
  31. 1349
  32. 921
  33. 540
  34. 883
  35. 1155
  36. 358
  37. 393
  38. 1013
  39. 123
  40. 488

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