How do you find the sum of the arithmetic sequence: 2,4,6,8,..., n = 20?
1 Answer
Mar 20, 2016
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
