The sum of the first terms n in the infinite geometric sequence {1/4, 1/8, 1/16, ..} is 15/32. Find n.
a = 1/4 (first term)
r = 1/2 (ratio)
n = number of terms
15/32 = 1/4((1/2)^n - 1)/(1/2 - 1)
Try to solve it by yourself from here. :))
15/8 = ((1/2)^n - 1)/(-1/2)
-15/16 = (1/2)^n - 1
1/16 = (1/2)^n
n = 4
=^._.^=
