The number of triangles that are formed by choosing the vertices from a set of 12 points, seven of which lie on the same line is
A. 105
B. 15
C. 175
D. 185
The answer is the option (d).
Number of ways of selecting 3 points from given 12 points=
But 3 points from given 7 collinear points does not form triangle.
Number of ways of selecting 3 points from seven collinear points=
Total number of triangles=