The straight lines L1,L2,L3 are parallel and lie in the same plane. A total
number of m points are taken on L1,n points on L2, k points on L3. The
maximum number of triangles formed with vertices at these points are
Total number of points are m+n+k, the â–³'s formed by these points = m+n+kC3
Joining 3 points on the same line gives no triangle, such â–³'s are mC3+nC3+kC3
∴ required number of triangle so formed=m+n+kC3−mC3−nC3−kC3