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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 255 · 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. 1.834 − 323 =
  2. 2.611 − 134 =
  3. 3.306 + 631 =
  4. 4.349 + 234 =
  5. 5.893 − 729 =
  6. 6.607 + 438 =
  7. 7.924 − 651 =
  8. 8.441 − 135 =
  9. 9.353 + 617 =
  10. 10.216 + 269 =
  11. 11.929 − 718 =
  12. 12.203 + 291 =
  13. 13.644 − 119 =
  14. 14.422 + 379 =
  15. 15.459 + 635 =
  16. 16.706 − 504 =
  17. 17.957 − 591 =
  18. 18.313 + 222 =
  19. 19.194 + 473 =
  20. 20.217 + 591 =
  21. 21.297 + 208 =
  22. 22.518 − 194 =
  23. 23.637 + 225 =
  24. 24.608 + 417 =
  25. 25.881 − 701 =
  26. 26.582 + 513 =
  27. 27.680 − 351 =
  28. 28.796 − 339 =
  29. 29.425 − 116 =
  30. 30.532 − 158 =
  31. 31.279 + 221 =
  32. 32.515 + 271 =
  33. 33.446 − 258 =
  34. 34.207 + 268 =
  35. 35.531 − 203 =
  36. 36.500 − 261 =
  37. 37.711 + 231 =
  38. 38.260 + 622 =
  39. 39.312 + 193 =
  40. 40.927 − 409 =

Answer key

  1. 511
  2. 477
  3. 937
  4. 583
  5. 164
  6. 1045
  7. 273
  8. 306
  9. 970
  10. 485
  11. 211
  12. 494
  13. 525
  14. 801
  15. 1094
  16. 202
  17. 366
  18. 535
  19. 667
  20. 808
  21. 505
  22. 324
  23. 862
  24. 1025
  25. 180
  26. 1095
  27. 329
  28. 457
  29. 309
  30. 374
  31. 500
  32. 786
  33. 188
  34. 475
  35. 328
  36. 239
  37. 942
  38. 882
  39. 505
  40. 518

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