Question

ABCDE is a Pentagon. How many triangles will you get if you join the point A to the remaining points
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Answer 1

Answer:

ABCDE is a regular pentagon with F at its center. How many different triangles can be formed by joining 3 of the points A,B,C,D,E and F?

(A) 10

(B) 15

(C) 20

(D) 25

(E) 30

Regular pentagon is a pentagon where all sides are equal. In such pentagon center is not collinear to any two vertices, so ANY three points (from 5 vertices and center point) WILL form the triangle.

The question basically asks how many triangles can be formed from the six points on a plane with no three points being collinear.

As any 3 points from 6 will make a triangle (since no 3 points are collinear), then:

6C3=20

Answer: C.

Hope it helps.