question_answer

The sum of the series \[1+2\times 3+3\times 5+4\times 7+....\] upto 11th term is :-             [JEE Main 9-4-2019 Afternoon]

A) 915                 

B) 946

C) 945                 

D) 916

Correct Answer: B

Solution :

\[{{T}_{r}}=r(2r-1)\]           \[S=\Sigma 2{{r}^{2}}-\Sigma r\]           \[S=\frac{2.n(n+1)(2n+1)}{6}-\frac{n(n+1)}{2}\]                     \[(44)(23)-66=946\]