Find the number of straight lines and triangles that can be formed out of 20 points of which 8 are collinear.
Number of straight lines
= 20C2 – 8C2 + 1 = 190 – 28 + 1
= 163 straight lines.
Number of triangles = 20C3 – 8C3
= 1140 – 56 = 1084.
