What is the sum of the finite arithmetic series 4+8+12+16 ... + 76

A (n) = 4+4 (n-1)

a (n) = 4+4n-4

a (n) = 4n

76=4n

n=19

The sum of any arithmetic sequence (series are infinite) is:

(a+a (n)) (n/2)

The average of the first and last terms times the number of terms, in this case we found that n=19 so:

19 (4+76) / 2=760