Permutations And Combinations Question 60

Question: The number of diagonals in a polygon of $ m $ sides is [BIT 1992; MP PET 1999; UPSEAT 1999; DCE 1999; Pb. CET 2001]

Options:

A) $ \frac{1}{2\ !}m(m-5) $

B) $ \frac{1}{2\ !}m(m-1) $

C) $ \frac{1}{2\ !}m(m-3) $

D) $ \frac{1}{2\ !}m(m-2) $

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Answer:

Correct Answer: C

Solution:

  • Required number of diagonals = $ ^{m}C_2-m $ $ =\frac{m(m-1)}{2!}-m=\frac{m}{2!}(m-3) $ .