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JEE MATHEMATICS MCQ: PERMUTATIONS

1 Easy

1 of 1

Application +4 | -1

Let

\mathrm{T}_4

denotes the number of triangles which can be formed by using the vertices of a regular polygon of

n

sides, If

T_{n+1}-T_n=21

, then

n

equals.

View answer and explanation

Correct option: A

7

Option A (7) is correct because solving the equation

T_{n+1} - T_n = 21

where

T_n = nC3

leads to n = 7.

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