# An arithmetic series has a common difference of 7. Given that the sum of the first 20 terms of the series is 530, how do you find the first term of the series?

##### 1 Answer

Mar 28, 2016

#### Explanation:

With the first term as a and common difference d, the sum for n terms =

Here, n = 20 and d = 7.

20a + ((19)(20)/2)7 = 530