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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 342 · 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. 1.689 − 484 =
  2. 2.636 + 179 =
  3. 3.935 − 623 =
  4. 4.576 + 284 =
  5. 5.685 + 164 =
  6. 6.563 − 172 =
  7. 7.948 − 182 =
  8. 8.170 + 616 =
  9. 9.575 + 689 =
  10. 10.328 + 278 =
  11. 11.796 − 632 =
  12. 12.272 + 605 =
  13. 13.625 + 314 =
  14. 14.435 − 316 =
  15. 15.736 − 204 =
  16. 16.455 − 135 =
  17. 17.622 + 451 =
  18. 18.256 + 601 =
  19. 19.878 − 357 =
  20. 20.560 + 339 =
  21. 21.138 + 576 =
  22. 22.824 − 496 =
  23. 23.316 + 291 =
  24. 24.632 + 546 =
  25. 25.562 − 323 =
  26. 26.224 + 249 =
  27. 27.327 + 578 =
  28. 28.765 − 522 =
  29. 29.917 − 631 =
  30. 30.648 − 198 =
  31. 31.870 − 601 =
  32. 32.499 − 224 =
  33. 33.560 + 678 =
  34. 34.669 + 471 =
  35. 35.234 + 291 =
  36. 36.987 − 155 =
  37. 37.198 + 408 =
  38. 38.405 + 414 =
  39. 39.979 − 236 =
  40. 40.442 − 131 =

Answer key

  1. 205
  2. 815
  3. 312
  4. 860
  5. 849
  6. 391
  7. 766
  8. 786
  9. 1264
  10. 606
  11. 164
  12. 877
  13. 939
  14. 119
  15. 532
  16. 320
  17. 1073
  18. 857
  19. 521
  20. 899
  21. 714
  22. 328
  23. 607
  24. 1178
  25. 239
  26. 473
  27. 905
  28. 243
  29. 286
  30. 450
  31. 269
  32. 275
  33. 1238
  34. 1140
  35. 525
  36. 832
  37. 606
  38. 819
  39. 743
  40. 311

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