Let ABC be a triangle. Consider four points , on the side AB , five points on the side BC and four points on the side AC . None of these points is a vertex of the triangle ABC . Then the total number of pentagons, that can be formed by taking all the vertices from the points , is ____ .
Answer: 660
Solution
A pentagon uses five of the thirteen points with no three collinear, so at most two may be taken from any one side. Five points split as across the sides in the three ways Hence pentagons can be formed.
JEE Main · 2026 · 22 Jan 2026 · Shift 1 · Integer answer