ABCD is a rectangle. Excluding the four vertices, there are four points each on AB and CD, and three points each on BC and AD. Find the number of triangles that can be formed using the 18 points.324361528756

To solve this problem, we need to understand that a triangle is formed by choosing any 3 points. Since we have 18 points in total, the number of triangles that can be formed is the number of ways to choose 3 points out of 18.

This can be calculated using the combination formula: C(n, r) = n! / [(n-r)! * r!], where n is the total number of items, r is the number of items to choose, and "!" denotes factorial.

Here, n = 18 (total points) and r = 3 (points to form a triangle).

So, the number of triangles = C(18, 3) = 18! / [(18-3)! * 3!] = 816.

Therefore, 816 triangles can be formed using the 18 points.