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shilpaqueen
- Junior | Next Rank: 30 Posts
- Posts: 19
- Joined: Thu Jul 29, 2010 2:12 am
How many triangles can be formed using 8 points in a given plane when 3 points out of 8 are collinier
By joining any 3 non collinear points, we get a triangle.
Had all 8 points been non collinear, the number of ways triangles would have been 8C3 which is 56.
But since 3 points are collinear, they will not make a triangle.
So the number of triangles we can have is 56 - 1 = 55.
