Question

Consider the $5$ points comprising of vertices of a square and the intersection point of its diagonals. Then the number of triangles that can be formed using these points are

Answer 1

To form a triangle, $3$ points out of $5$ can be chosen in ${}^5{C}_3=10$ ways.
But out of these, the three points lying on the $2$ diagonals will be collinear.
$\therefore$ $10-2=8$ triangles can be formed