What is the sum of the first 9 terms of an ar | vedclass

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(D) Given:First term $(a)$ = $7$Last term $(l)$ = $55$Number of terms $(n)$ = $9$The formula for the sum of the first $n$ terms of an arithmetic progr

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$279$

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(D) Given:First term $(a)$ = $7$Last term $(l)$ = $55$Number of terms $(n)$ = $9$The formula for the sum of the first $n$ terms of an arithmetic progression when the first and last terms are known is:$S_n = \frac{n}{2}(a + l)$Substituting the given values:$S_9 = \frac{9}{2}(7 + 55)$$S_9 = \frac{9}{2}(62)$$S_9 = 9 	imes 31$$S_9 = 279$

What is the sum of the first $9$ terms of an arithmetic progression if the first term is $7$ and the last term is $55$?

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