The number of triangles that can be formed by choosing the vertices from a set of 12 points, seven of which lie on the same straight line, is
185
175
115
105
Required number of ways = 12C3−7C3
= 220 - 35 = 185
There are 10 points in a plane no three of which are in the same straight line, excepting 4 points, which are collinear.
Find the probability that
(i) number of straight lines obtained from the pairs of these points.
(ii) number of triangles that can be formed with the vertices as these points.