# What is the sum of the arithmetic sequence 308, 304, 300, …, if there are 25 terms?

Jan 13, 2016

6500

#### Explanation:

Sum of an arithmetic series = $\frac{n}{2} \left(2 a + \left(n - 1\right) d\right)$
where a = first term, n = number of terms, d = common difference

Sum = $\frac{25}{2} \left(2 \cdot 308 + 24 \cdot \left(- 4\right)\right)$
$= 12.5 \left(616 - 96\right)$
$= 12.5 \cdot 520$
$= 6500$