2024 DMC Mock 10 Problems/Problem 11

Revision as of 12:10, 22 December 2024 by Pateywatey (talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

First we use complementary counting to count the total number of possibilities. There are $4! = 24$ ways to arrange the officers without restrictions, and $2 \cdot 6! = 12$ ways if the treasurer and president sit next to each other, so the officers can sit in a total of $24 - 12 = 12$ ways. Similarly, there are $4$ ways for both the treasurer and vice president to sit next to the president. Therefore, the answer is $\frac{12-4}{12}=\boxed{\frac{2}{3}}$.