If the first term of an A.P. is 2 and common difference is 4, then the sum of its 40 term is
A. 3200 B. 1600 C. 200 D. 2800 Answer: Option AShow Answer
Solution(By Apex Team)
$\begin{aligned}&\text{ In an A.P. }\\
&a=2\text{ and }d=4,n=40\\
&\therefore S_n=\frac{n}{2}[2a+(n-1)d]\\
&=\frac{40}{2}[2\times2+(40-1)\times4]\\
&=20[4+39\times4]\\
&=20\times(4+156)\\
&=20\times160\\
&=3200\end{aligned}$
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