Question

Permutations and Combination in 11


Find the number of diagnols if sides = 16

Answer 1

no of diagonals is 16C2-16
=104

Answer 2

Hey!
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★Permutations and Combinations ★
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Ques.→ Find the number of diagnols if the number of sides in a polygon = 16.


Ans. → Given that , n = 16 .

•Now two verticess are joined to form a diagnol so ,



=> Number of diagnols + Number of Sides = 16 C 2


=> d + 16 = 16! / 2! 14! { as nCr = n! / r! ( n - r )! }


=> d + 16 = 16 × 15 × 14! / 2 × 1 × 14!


=> d + 16 = 120


•°• d = 104 ✔


→ Thus, the polygon has 104 diagnols. !!

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