Hello, greghunter!

You're expected to know this formula:

. .

We have: .The first term of an arithmetic series is 16 and the last is 60.

The sum of the arithmetic series is 342. .Find the common difference.

Then: .

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

If you didn't know that formula, you can still work it out.

First term: . .[1]

Last term: . .[2]

Sum of the first n terms: . .[3]

Substitute [1] and [2] into [3]: .

. . . . . See?