Let\[{{T}_{n}}\]be the number of all possible triangles formed by joining vertices of a n−sided regular polygon. If\[{{T}_{n+1}}-{{T}_{n}}=1\]then the value of n is:
AIEEE Solevd Paper-2013
A)7
B)5
C) 10
D) 8
Correct Answer:
B
Solution :
\[^{n+1}{{C}_{3}}{{-}^{n}}{{C}_{3}}=10\] On solving n = 5