Question

What is the first term of a geometric series with a summation of 800, 4 terms and a common ratio of 3?

Answer 1

easy way:
1,3,9,27 adds to 40
800/40 = 20

so, 20,60,180,540

or,

a(1+r+r^2+r^3) = a(r^4-1)/(r-1) = a*80/2 = 40a

so, a = 800/40 = 20

Answer 2

Thank you, I think I understand how to work it out now! That helped me out so much!