A, B, C, D and E are coplanar points and three of them lie in a straight line. What is the maximum number of triangles that can be drawn with these points as their vertices?

Step-by-step solution

Total number of points =5 Now a triangle has three vertices Number of triangles forms =5 c₃ But it is given that three points are collinear. So that maximum number of triangles formed =5 c₃-3 c₃= 5 4 2 -1=10-1=9