JEE Main 2015MathematicsPermutation CombinationMediumMCQ

JEE Main 2015 — Permutation Combination Question with Solution

JEE Main 2015 (11 Apr Online)

Question

If in a regular polygon the number of diagonals is 54, then the number of sides of this polygon is:

Choose an option

Show full solutionCorrect option: A
Correct answer
A12

Step-by-step explanation

Number of diagonals of an ′n′ sided polygon is

 nC2 -n=54

nn-11.2-n=54

n2-n2-n=54

n2 -3n = 108

n2-3n-108=0

n-12n+9=0

n=12

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About this question

This is a previous-year question from JEE Main 2015, covering the Permutation Combination chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.