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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 A
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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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