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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 910 · 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. 1.517 + 221 =
  2. 2.171 + 273 =
  3. 3.717 + 533 =
  4. 4.412 + 239 =
  5. 5.847 − 745 =
  6. 6.509 − 122 =
  7. 7.745 + 374 =
  8. 8.748 − 176 =
  9. 9.545 − 263 =
  10. 10.292 + 688 =
  11. 11.553 + 403 =
  12. 12.357 + 585 =
  13. 13.571 + 428 =
  14. 14.442 + 176 =
  15. 15.981 − 131 =
  16. 16.223 + 534 =
  17. 17.657 − 413 =
  18. 18.591 + 617 =
  19. 19.727 + 488 =
  20. 20.988 − 304 =
  21. 21.934 − 675 =
  22. 22.752 − 267 =
  23. 23.876 − 535 =
  24. 24.460 + 669 =
  25. 25.739 + 258 =
  26. 26.640 + 423 =
  27. 27.359 + 517 =
  28. 28.297 + 631 =
  29. 29.977 − 724 =
  30. 30.694 − 366 =
  31. 31.727 + 259 =
  32. 32.218 + 609 =
  33. 33.204 + 337 =
  34. 34.516 − 309 =
  35. 35.301 + 562 =
  36. 36.838 − 551 =
  37. 37.985 − 241 =
  38. 38.162 + 281 =
  39. 39.982 − 797 =
  40. 40.780 + 281 =

Answer key

  1. 738
  2. 444
  3. 1250
  4. 651
  5. 102
  6. 387
  7. 1119
  8. 572
  9. 282
  10. 980
  11. 956
  12. 942
  13. 999
  14. 618
  15. 850
  16. 757
  17. 244
  18. 1208
  19. 1215
  20. 684
  21. 259
  22. 485
  23. 341
  24. 1129
  25. 997
  26. 1063
  27. 876
  28. 928
  29. 253
  30. 328
  31. 986
  32. 827
  33. 541
  34. 207
  35. 863
  36. 287
  37. 744
  38. 443
  39. 185
  40. 1061

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