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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 817 · 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. 1.593 + 137 =
  2. 2.695 + 406 =
  3. 3.283 + 257 =
  4. 4.346 + 234 =
  5. 5.430 + 288 =
  6. 6.937 − 718 =
  7. 7.777 + 348 =
  8. 8.307 + 458 =
  9. 9.505 + 633 =
  10. 10.162 + 586 =
  11. 11.193 + 403 =
  12. 12.726 + 627 =
  13. 13.815 − 497 =
  14. 14.540 + 428 =
  15. 15.787 + 378 =
  16. 16.520 − 264 =
  17. 17.519 + 681 =
  18. 18.940 − 559 =
  19. 19.129 + 339 =
  20. 20.711 + 263 =
  21. 21.491 − 178 =
  22. 22.665 − 564 =
  23. 23.779 + 212 =
  24. 24.781 − 625 =
  25. 25.579 − 332 =
  26. 26.313 + 225 =
  27. 27.209 + 634 =
  28. 28.866 − 151 =
  29. 29.440 + 173 =
  30. 30.428 − 152 =
  31. 31.132 + 464 =
  32. 32.775 + 668 =
  33. 33.583 + 617 =
  34. 34.400 + 137 =
  35. 35.132 + 364 =
  36. 36.664 + 177 =
  37. 37.729 − 153 =
  38. 38.837 − 664 =
  39. 39.435 + 126 =
  40. 40.457 − 241 =

Answer key

  1. 730
  2. 1101
  3. 540
  4. 580
  5. 718
  6. 219
  7. 1125
  8. 765
  9. 1138
  10. 748
  11. 596
  12. 1353
  13. 318
  14. 968
  15. 1165
  16. 256
  17. 1200
  18. 381
  19. 468
  20. 974
  21. 313
  22. 101
  23. 991
  24. 156
  25. 247
  26. 538
  27. 843
  28. 715
  29. 613
  30. 276
  31. 596
  32. 1443
  33. 1200
  34. 537
  35. 496
  36. 841
  37. 576
  38. 173
  39. 561
  40. 216

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