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IRINA_888 [86]
3 years ago
11

How many triangles and quadrilaterals altogether can be formed using the vertices of a 7-sided regular polygon?

Mathematics
1 answer:
MAVERICK [17]3 years ago
8 0

Answer:  The correct option is

(E) 70.

Step-by-step explanation:  We are given to find the number of  triangles and quadrilaterals altogether that can be formed using the vertices of a 7-sided regular polygon.

To form a triangle, we need any 3 vertices of the 7-sided regular polygon. So, the number of triangles that can be formed is

n_t=^7C_3=\dfrac{7!}{3!(7-3)!}=\dfrac{7\times6\times5\times4!}{3\times2\times1\times4!}=35.

Also, to form a quadrilateral, we need any 4 vertices of the 7-sided regular polygon. So, the number of quadrilateral that can be formed is

n_q=^7C_4=\dfrac{7!}{4!(7-4)!}=\dfrac{7\times6\times5\times4!}{4!\times3\times2\times1}=35.

Therefore, the total number of triangles and quadrilaterals is

n=n_t+n_q=35+35=70.

Thus, option (E) is CORRECT.

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