# Help with Sequences and Series Problem

• May 26th 2013, 04:01 PM
Espionage
Help with Sequences and Series Problem
The sum of the first twelve terms of an arithmetic sequence of real numbers is 60. The first term is -6. What is the sum of the first twenty terms?
• May 26th 2013, 04:20 PM
Plato
Re: Help with Sequences and Series Problem
Quote:

Originally Posted by Espionage
The sum of the first twelve terms of an arithmetic sequence of real numbers is 60. The first term is -6. What is the sum of the first twenty terms?

Suppose that $S_n$ is the sum of the first n terms and d is the common difference then $S_n=a+(n-1)d$ where $a$ is the first term.
• May 26th 2013, 04:49 PM
Espionage
Re: Help with Sequences and Series Problem
Thank you very much.