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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 864 · 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. 1.532 + 465 =
  2. 2.834 − 535 =
  3. 3.717 + 652 =
  4. 4.275 + 352 =
  5. 5.323 + 255 =
  6. 6.508 − 325 =
  7. 7.813 − 421 =
  8. 8.500 + 455 =
  9. 9.193 + 617 =
  10. 10.856 − 462 =
  11. 11.866 − 504 =
  12. 12.448 − 221 =
  13. 13.206 + 244 =
  14. 14.853 − 279 =
  15. 15.459 − 305 =
  16. 16.818 − 208 =
  17. 17.903 − 471 =
  18. 18.432 − 198 =
  19. 19.436 − 253 =
  20. 20.848 − 172 =
  21. 21.435 + 431 =
  22. 22.320 + 561 =
  23. 23.657 + 121 =
  24. 24.809 − 335 =
  25. 25.719 − 391 =
  26. 26.731 − 547 =
  27. 27.430 + 294 =
  28. 28.941 − 813 =
  29. 29.238 + 166 =
  30. 30.945 − 325 =
  31. 31.211 + 669 =
  32. 32.678 − 234 =
  33. 33.979 − 674 =
  34. 34.652 + 604 =
  35. 35.662 − 345 =
  36. 36.599 − 414 =
  37. 37.450 + 287 =
  38. 38.518 + 379 =
  39. 39.652 − 229 =
  40. 40.334 + 679 =

Answer key

  1. 997
  2. 299
  3. 1369
  4. 627
  5. 578
  6. 183
  7. 392
  8. 955
  9. 810
  10. 394
  11. 362
  12. 227
  13. 450
  14. 574
  15. 154
  16. 610
  17. 432
  18. 234
  19. 183
  20. 676
  21. 866
  22. 881
  23. 778
  24. 474
  25. 328
  26. 184
  27. 724
  28. 128
  29. 404
  30. 620
  31. 880
  32. 444
  33. 305
  34. 1256
  35. 317
  36. 185
  37. 737
  38. 897
  39. 423
  40. 1013

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