the sum of the first 6 terms of a geometric series is 15624 and the common ratio is 5. what is the first term of the series?

first term a=4

Step-by-step explanation:

Sum of the first 6 terms S6 = 15624

common ratio r = 5

n = 6

first term a=?

Formula: S6 = a (r^n-1) / r-1

15624 = a (5^6-1) / 5-1

15624 = a (15625-1) / 4

15624 = a (15624) : 4

15624 = 15624a:4

Cross multiply

15624*4 = 15624a

62496 = 15624a

divide both sides by 15624

62496:15624 = 15624a:15624

4 = a

a = 4