Count Number of Triangle
Level
pending
Known a triangle with vertices ABC. On line AB we add 3 vertices, on line BC add 3 vertices, and so on line AC add 3 vertices.
How many triangles we can make with all vertices?
The answer is 190.
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1 solution
First write possibility we can make by all vertices to make triangle (triple vertices) and it is 12C3 because there are 12 vertices. But we know that one line vertices can't make a triangle so it is minus by 5C3*3 which is the answer is 190.