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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 31 · 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. 1.586 + 679 =
  2. 2.692 − 549 =
  3. 3.662 − 406 =
  4. 4.544 − 366 =
  5. 5.599 − 394 =
  6. 6.177 + 593 =
  7. 7.583 − 306 =
  8. 8.234 + 229 =
  9. 9.771 − 491 =
  10. 10.862 − 547 =
  11. 11.786 + 395 =
  12. 12.249 + 213 =
  13. 13.831 − 598 =
  14. 14.269 + 541 =
  15. 15.866 − 701 =
  16. 16.759 + 494 =
  17. 17.418 + 532 =
  18. 18.571 + 198 =
  19. 19.447 + 487 =
  20. 20.400 + 503 =
  21. 21.285 + 392 =
  22. 22.657 + 619 =
  23. 23.345 + 251 =
  24. 24.518 − 303 =
  25. 25.451 − 137 =
  26. 26.504 + 469 =
  27. 27.462 + 336 =
  28. 28.754 + 536 =
  29. 29.229 + 146 =
  30. 30.510 − 376 =
  31. 31.737 − 428 =
  32. 32.181 + 526 =
  33. 33.526 + 321 =
  34. 34.513 + 371 =
  35. 35.945 − 327 =
  36. 36.912 − 287 =
  37. 37.917 − 271 =
  38. 38.759 − 341 =
  39. 39.705 + 343 =
  40. 40.454 + 437 =

Answer key

  1. 1265
  2. 143
  3. 256
  4. 178
  5. 205
  6. 770
  7. 277
  8. 463
  9. 280
  10. 315
  11. 1181
  12. 462
  13. 233
  14. 810
  15. 165
  16. 1253
  17. 950
  18. 769
  19. 934
  20. 903
  21. 677
  22. 1276
  23. 596
  24. 215
  25. 314
  26. 973
  27. 798
  28. 1290
  29. 375
  30. 134
  31. 309
  32. 707
  33. 847
  34. 884
  35. 618
  36. 625
  37. 646
  38. 418
  39. 1048
  40. 891

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