Question

$3+5+7+....$ to $n$ terms is

• A. $n(n+2)$
• B. $n(n-2)$
• C. $n^2$
• D. $(n+1{)}^2$

Answer 1

The correct option is A $n(n+2)$

$S=3+5+7+...$ upto $n$ terms
It is an A.P with $a=3,d=2$
$S_n=\frac{n}{2}(a+a_n)=\frac{n}{2}(3+3+(n-1)\times 2)$
$\Rightarrow S_n=n(n+2)$