# How do you find the sum of the arithmetic sequence: 2,4,6,8,..., n = 20?

##### 1 Answer

Mar 20, 2016

#### Answer:

420

#### Explanation:

For the general Arithmetic sequence , with terms

a , a+d , a+2d , a+3d , .................... , a + (n-1)d

where a is the 1st term and d , the common difference

The sum to n terms =

# n/2 [ 2a + (n-1)d) ] # here a = 2 , d = 4-2 = 6-4 = 2 and n = 20

sum of 1st 20 terms

# = 20/2 [ (2xx2) + (19xx2) ] = 420#