CEMC Fermat, 1998

Combinatorics Difficulty 2.0 Junior Find the answer Canada

Three-digit integers are formed using only the digits 1 and/or 2. The sum of all such integers formed is

(A) $1332$ (B) $333$ (C) $999$ (D) $666$ (E) $1665$

We don't reproduce this publisher's solutions. Their own solution is here — work the problem first.

Want a route through all this instead of an archive? The track puts 2,604 problems in a working order, from Junior Challenge level to the IMO shortlist.

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.