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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 10 · 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. 1.125 + 171 =
  2. 2.606 − 362 =
  3. 3.560 − 162 =
  4. 4.816 − 264 =
  5. 5.791 − 296 =
  6. 6.440 − 223 =
  7. 7.782 + 326 =
  8. 8.168 + 183 =
  9. 9.649 + 199 =
  10. 10.539 − 311 =
  11. 11.458 + 323 =
  12. 12.441 + 337 =
  13. 13.706 + 598 =
  14. 14.889 − 143 =
  15. 15.654 + 354 =
  16. 16.716 + 479 =
  17. 17.564 + 257 =
  18. 18.614 + 373 =
  19. 19.573 − 343 =
  20. 20.191 + 307 =
  21. 21.292 + 375 =
  22. 22.254 + 168 =
  23. 23.912 − 616 =
  24. 24.663 + 521 =
  25. 25.773 + 177 =
  26. 26.478 + 444 =
  27. 27.426 − 326 =
  28. 28.518 − 206 =
  29. 29.631 − 282 =
  30. 30.723 − 175 =
  31. 31.653 + 262 =
  32. 32.419 − 281 =
  33. 33.533 + 531 =
  34. 34.881 − 551 =
  35. 35.763 + 571 =
  36. 36.754 − 371 =
  37. 37.652 + 687 =
  38. 38.588 − 468 =
  39. 39.155 + 372 =
  40. 40.257 + 361 =

Answer key

  1. 296
  2. 244
  3. 398
  4. 552
  5. 495
  6. 217
  7. 1108
  8. 351
  9. 848
  10. 228
  11. 781
  12. 778
  13. 1304
  14. 746
  15. 1008
  16. 1195
  17. 821
  18. 987
  19. 230
  20. 498
  21. 667
  22. 422
  23. 296
  24. 1184
  25. 950
  26. 922
  27. 100
  28. 312
  29. 349
  30. 548
  31. 915
  32. 138
  33. 1064
  34. 330
  35. 1334
  36. 383
  37. 1339
  38. 120
  39. 527
  40. 618

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