### Home > CCG > Chapter 5 > Lesson 5.3.4 > Problem5-115

5-115.

How many terms are in the arithmetic sequence shown below?
$15$, $7$, $-1$, $-9$, $\dots$, $-225$

Remember that the equation for an arithmetic sequence is:

$a_{n}= m(n-1)+a_{1}$

Find the common difference. Substitute the common difference into m and substitute the first and last term into the equation.

$n$ is the number of terms.
Solve the equation for $n$.

$n=31$ terms