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JEE MATHEMATICS MCQ: COMBINATIONS

1 Easy

1 of 1

Application +4 | -1

Let

{T_n}

denote the number of triangles which can be formed 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: B

7

Option B (7) is correct because solving the equation

{T_{n + 1}} - {T_n} = 21

with

{T_n} = {\;^n}{C_3}

leads to n = 7.

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n