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There is a polygon of 10 sides. How many triangles can be drawn using the vertices of the polygon?
Question

There is a polygon of 10 sides. How many triangles can be drawn using the vertices of the polygon?

A.

120

B.

100

C.

150

D.

125

Correct option is A

Given:
Number of sides of the polygon = 10
Number of vertices of the polygon = 10
Formula Used:
Number of triangles that can be formed using n vertices is given by Combinations formula:
nC3=n!3!×(n3)!=n×(n1)×(n2)3×2×1^{n}C_{3} = \frac{n!}{3! × (n-3)!} = \frac{n × (n-1) × (n-2)}{3 × 2 × 1}​​
Solution:
A triangle is formed by joining any 3 non-collinear vertices.
Since all vertices of a polygon are points on its circumference (if cyclic) or lie in a way that no three consecutive vertices are collinear, we choose any 3 vertices out of the available 10 vertices.
Here, n = 10.
Number of triangles = 10C3 ^{10}C_{3}​​
Number of triangles = 10×9×83×2×1 \frac{10 × 9 × 8}{3 × 2 × 1}​​
Number of triangles = 120
Final Answer
So the correct answer is (a)

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