The sum of the first n terms in the infinite geometric sequence {1, 1/3, 1/9, 1/27, ...} is 364/243. Find n.

formula for sum of geometric series is S(n) = (a_1*(1-r^n))/1-r where r is not equal to 1. use it

Expand the sequence:

1, 1/3, 1/9, 1/27, 1/81, 1/243. If you sum them up, you should get =364 / 243. Therefore, just count the number of terms, which = 6 terms.