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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 49 · 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. 1.351 + 401 =
  2. 2.929 − 382 =
  3. 3.645 + 467 =
  4. 4.464 + 664 =
  5. 5.545 − 165 =
  6. 6.641 − 204 =
  7. 7.612 + 553 =
  8. 8.337 + 252 =
  9. 9.253 + 177 =
  10. 10.580 − 361 =
  11. 11.442 − 281 =
  12. 12.575 + 588 =
  13. 13.463 − 167 =
  14. 14.154 + 257 =
  15. 15.314 + 301 =
  16. 16.451 − 229 =
  17. 17.480 − 381 =
  18. 18.483 − 222 =
  19. 19.661 + 427 =
  20. 20.491 − 349 =
  21. 21.222 + 321 =
  22. 22.255 + 564 =
  23. 23.571 − 344 =
  24. 24.337 + 527 =
  25. 25.474 − 242 =
  26. 26.721 − 161 =
  27. 27.947 − 845 =
  28. 28.148 + 433 =
  29. 29.974 − 535 =
  30. 30.239 + 521 =
  31. 31.693 − 166 =
  32. 32.567 + 389 =
  33. 33.937 − 409 =
  34. 34.537 − 388 =
  35. 35.163 + 284 =
  36. 36.363 + 596 =
  37. 37.845 − 231 =
  38. 38.439 + 542 =
  39. 39.492 + 221 =
  40. 40.382 + 133 =

Answer key

  1. 752
  2. 547
  3. 1112
  4. 1128
  5. 380
  6. 437
  7. 1165
  8. 589
  9. 430
  10. 219
  11. 161
  12. 1163
  13. 296
  14. 411
  15. 615
  16. 222
  17. 99
  18. 261
  19. 1088
  20. 142
  21. 543
  22. 819
  23. 227
  24. 864
  25. 232
  26. 560
  27. 102
  28. 581
  29. 439
  30. 760
  31. 527
  32. 956
  33. 528
  34. 149
  35. 447
  36. 959
  37. 614
  38. 981
  39. 713
  40. 515

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