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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 389 · 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. 1.263 + 135 =
  2. 2.463 + 287 =
  3. 3.445 + 121 =
  4. 4.844 − 432 =
  5. 5.610 + 231 =
  6. 6.633 + 631 =
  7. 7.381 + 486 =
  8. 8.819 − 661 =
  9. 9.286 + 649 =
  10. 10.585 − 295 =
  11. 11.473 − 151 =
  12. 12.707 − 367 =
  13. 13.551 − 287 =
  14. 14.629 + 642 =
  15. 15.493 + 684 =
  16. 16.626 + 651 =
  17. 17.402 + 381 =
  18. 18.450 − 148 =
  19. 19.141 + 646 =
  20. 20.459 − 304 =
  21. 21.413 − 152 =
  22. 22.444 − 261 =
  23. 23.435 + 373 =
  24. 24.525 + 308 =
  25. 25.685 − 372 =
  26. 26.826 − 695 =
  27. 27.765 − 446 =
  28. 28.716 + 417 =
  29. 29.406 + 311 =
  30. 30.742 + 495 =
  31. 31.162 + 121 =
  32. 32.799 − 571 =
  33. 33.716 − 562 =
  34. 34.859 − 148 =
  35. 35.696 + 151 =
  36. 36.682 − 285 =
  37. 37.730 + 671 =
  38. 38.249 + 308 =
  39. 39.501 − 326 =
  40. 40.685 + 605 =

Answer key

  1. 398
  2. 750
  3. 566
  4. 412
  5. 841
  6. 1264
  7. 867
  8. 158
  9. 935
  10. 290
  11. 322
  12. 340
  13. 264
  14. 1271
  15. 1177
  16. 1277
  17. 783
  18. 302
  19. 787
  20. 155
  21. 261
  22. 183
  23. 808
  24. 833
  25. 313
  26. 131
  27. 319
  28. 1133
  29. 717
  30. 1237
  31. 283
  32. 228
  33. 154
  34. 711
  35. 847
  36. 397
  37. 1401
  38. 557
  39. 175
  40. 1290

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