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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 72 · 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. 1.349 + 539 =
  2. 2.284 + 541 =
  3. 3.722 − 181 =
  4. 4.468 − 204 =
  5. 5.446 − 113 =
  6. 6.152 + 637 =
  7. 7.265 + 206 =
  8. 8.270 + 578 =
  9. 9.884 − 173 =
  10. 10.485 + 123 =
  11. 11.941 − 779 =
  12. 12.432 + 223 =
  13. 13.515 + 194 =
  14. 14.773 − 288 =
  15. 15.771 − 575 =
  16. 16.871 − 644 =
  17. 17.137 + 686 =
  18. 18.253 + 243 =
  19. 19.803 − 243 =
  20. 20.306 + 483 =
  21. 21.681 − 254 =
  22. 22.661 + 265 =
  23. 23.867 − 491 =
  24. 24.282 + 449 =
  25. 25.877 − 303 =
  26. 26.496 − 368 =
  27. 27.932 − 399 =
  28. 28.947 − 498 =
  29. 29.422 − 173 =
  30. 30.837 − 671 =
  31. 31.533 + 616 =
  32. 32.443 − 311 =
  33. 33.751 − 201 =
  34. 34.795 − 348 =
  35. 35.344 + 465 =
  36. 36.601 + 337 =
  37. 37.625 + 685 =
  38. 38.649 − 429 =
  39. 39.640 − 375 =
  40. 40.499 + 594 =

Answer key

  1. 888
  2. 825
  3. 541
  4. 264
  5. 333
  6. 789
  7. 471
  8. 848
  9. 711
  10. 608
  11. 162
  12. 655
  13. 709
  14. 485
  15. 196
  16. 227
  17. 823
  18. 496
  19. 560
  20. 789
  21. 427
  22. 926
  23. 376
  24. 731
  25. 574
  26. 128
  27. 533
  28. 449
  29. 249
  30. 166
  31. 1149
  32. 132
  33. 550
  34. 447
  35. 809
  36. 938
  37. 1310
  38. 220
  39. 265
  40. 1093

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