Question

find the sum, ( s_n ), for the arithmetic series described? remember to use the formula ( s_n = \frac{n}{2}(a_1 + a_n) ) where ( a_1 = 8 ), ( a_n = 79 ), ( n = 6 ).
( circ ) a. ( s_n = 522 )
( circ ) b. ( s_n = 213 )
( circ ) c. ( s_n = 261 )
( circ ) d. ( s_n = 498 )

Explanation:

Step1: Substitute values into formula

Substitute $a_1=8$, $a_n=79$, $n=6$ into $S_n=\frac{n}{2}(a_1+a_n)$:
$S_6=\frac{6}{2}(8+79)$

Step2: Simplify the expression

First calculate $\frac{6}{2}=3$, then $8+79=87$:
$S_6=3\times87$

Step3: Compute final product

Calculate the multiplication:
$S_6=261$

Answer:

c. $S_n$=261