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What is the sum of the first 13 terms of an arithmetic progression if the first term is -10 and last term is 26?

A. 104 B. 140 C. 84 D. 98 Answer: Option A
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Solution(By Apex Team)

$\begin{aligned}&S_n=\frac{n}{2}[a+l]\\ &S_{13}=\frac{13}{2}[-10+26]\\ &S_{13}=\frac{13}{2}[16]\\ &S_{13}=104\end{aligned}$

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