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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 765 · 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. 1.253 + 144 =
  2. 2.552 − 428 =
  3. 3.338 + 468 =
  4. 4.209 + 143 =
  5. 5.704 + 651 =
  6. 6.437 + 201 =
  7. 7.795 − 555 =
  8. 8.695 − 316 =
  9. 9.573 + 419 =
  10. 10.192 + 483 =
  11. 11.853 − 689 =
  12. 12.353 + 141 =
  13. 13.525 + 372 =
  14. 14.917 − 172 =
  15. 15.645 − 483 =
  16. 16.680 + 171 =
  17. 17.522 + 677 =
  18. 18.739 − 122 =
  19. 19.722 + 621 =
  20. 20.879 − 586 =
  21. 21.419 + 526 =
  22. 22.564 + 507 =
  23. 23.459 − 122 =
  24. 24.592 + 277 =
  25. 25.467 + 382 =
  26. 26.163 + 218 =
  27. 27.503 + 581 =
  28. 28.661 + 541 =
  29. 29.152 + 607 =
  30. 30.753 + 266 =
  31. 31.476 − 137 =
  32. 32.313 + 142 =
  33. 33.309 + 459 =
  34. 34.125 + 421 =
  35. 35.961 − 795 =
  36. 36.308 + 616 =
  37. 37.523 + 607 =
  38. 38.638 + 403 =
  39. 39.472 − 205 =
  40. 40.740 + 233 =

Answer key

  1. 397
  2. 124
  3. 806
  4. 352
  5. 1355
  6. 638
  7. 240
  8. 379
  9. 992
  10. 675
  11. 164
  12. 494
  13. 897
  14. 745
  15. 162
  16. 851
  17. 1199
  18. 617
  19. 1343
  20. 293
  21. 945
  22. 1071
  23. 337
  24. 869
  25. 849
  26. 381
  27. 1084
  28. 1202
  29. 759
  30. 1019
  31. 339
  32. 455
  33. 768
  34. 546
  35. 166
  36. 924
  37. 1130
  38. 1041
  39. 267
  40. 973

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