Consider a polygon of sides 'n' which satisfies the equation `3*.^(n)P_(4)=.^(n-1)P_(5)`.
Q. Number of quadrilaterals that can be made using the vertices of the polygon of sides 'n' if exactly two adjacent sides of the quadrilateral are common to the sides of the n-gon is

Options

A. 50
B. 60
C. 70
D. 80

Answer

A

Explanation

Number of quadrilaterals of which exactly two adjacent sides of the quadrilateral are common to the sides of the n-gon
`=nxx.^(n-5)C_(1)=n(n-5)=10xx5" "[becausen=10]`
`=50`