There are 12 points in a plane, no three of which are in the same straight line, except 5 points which are collinear. Then the total number of triangles that can be formed with the vertices at any three of these 12 points is [2025]
(2)
The number of ways to choose 3 points from 12 =
= = 220
Number of ways to choose 3 points from 5 collinear points = = 10
Since these 5 points are collinear, so they can not form any triangles.
Number of triangles that can be formed = 220 –10 = 210