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CEMC Gauss (Grade 7), 2008

Combinatorics Difficulty 2.0 Junior Find the answer Canada

There are $24$ ways in which Beverly, Dianne, Ethan, and Jamaal can arrange themselves to sit in a row of four seats. In how many ways can Beverly, Dianne, Ethan, and Jamaal arrange themselves in a row of four seats so that Ethan does not sit beside Dianne?

(A) $18$ (B) $12$ (C) $21$ (D) $6$ (E) $15$

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