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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 344 · 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. 1.424 − 145 =
  2. 2.789 + 403 =
  3. 3.972 − 376 =
  4. 4.443 − 151 =
  5. 5.436 − 232 =
  6. 6.774 + 175 =
  7. 7.206 + 484 =
  8. 8.555 + 617 =
  9. 9.198 + 658 =
  10. 10.459 − 196 =
  11. 11.642 − 299 =
  12. 12.695 − 272 =
  13. 13.570 + 205 =
  14. 14.681 − 241 =
  15. 15.733 + 118 =
  16. 16.567 + 131 =
  17. 17.446 + 554 =
  18. 18.216 + 651 =
  19. 19.597 + 611 =
  20. 20.967 − 555 =
  21. 21.336 + 652 =
  22. 22.260 + 323 =
  23. 23.652 + 124 =
  24. 24.596 + 542 =
  25. 25.123 + 407 =
  26. 26.379 + 596 =
  27. 27.459 − 341 =
  28. 28.737 − 247 =
  29. 29.867 − 567 =
  30. 30.415 − 309 =
  31. 31.310 + 344 =
  32. 32.505 − 166 =
  33. 33.498 − 338 =
  34. 34.523 − 152 =
  35. 35.540 + 356 =
  36. 36.844 − 529 =
  37. 37.751 + 206 =
  38. 38.520 − 316 =
  39. 39.370 + 641 =
  40. 40.248 + 241 =

Answer key

  1. 279
  2. 1192
  3. 596
  4. 292
  5. 204
  6. 949
  7. 690
  8. 1172
  9. 856
  10. 263
  11. 343
  12. 423
  13. 775
  14. 440
  15. 851
  16. 698
  17. 1000
  18. 867
  19. 1208
  20. 412
  21. 988
  22. 583
  23. 776
  24. 1138
  25. 530
  26. 975
  27. 118
  28. 490
  29. 300
  30. 106
  31. 654
  32. 339
  33. 160
  34. 371
  35. 896
  36. 315
  37. 957
  38. 204
  39. 1011
  40. 489

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