Let $\mathscr { A }$ be the set of all $3 \times 3$ symmetric matrices all of whose entries are either 0 or 1. Five of these entries are 1 and four of them are 0. The number of matrices in $\mathscr { A }$ is (A) 12 (B) 6 (C) 9 (D) 3
Let $\mathscr { A }$ be the set of all $3 \times 3$ symmetric matrices all of whose entries are either 0 or 1. Five of these entries are 1 and four of them are 0.
The number of matrices in $\mathscr { A }$ is\\
(A) 12\\
(B) 6\\
(C) 9\\
(D) 3