Question 1094688
<pre>
Starting with the 2nd term divide each term by the preceding term:

15/5 = 3
45/15 = 3
135/45 = 3
405/135 = 3

Since they are all the same, that shows that it is a geometric series 
with first term a<sub>1</sub> = 5, common ratio r = 3, and number of terms n = 14.

The formula for the sum S<sub>n</sub> of a geometric series with first 
term a<sub>1</sub>, common ratio r, and number of terms n is:

{{{S[n]}}}{{{""=""}}}{{{a[1](r^n-1)/(r-1)}}}

Plugging in a<sub>1</sub> = 5, r = 3, and n = 14 into the formula:

{{{S[14]}}}{{{""=""}}}{{{(5)(3^14-1)/(3-1)}}}

You simplify that.  The answer is an 8-digit number

Edwin</pre>