Question

The school store started selling music CDs five years ago. They sold $22,600 worth in the first year. But, since MP3 players became so popular, the total yearly sales of CDs have dropped 14% per year since then. What is the total money collected for music CDs sold in the school store over the last five years? Use the geometric series formula to calculate your answer.

Answer 1

The sum of geometric series is given by:
Sn=a(1-r^n)/(1-r)
a= first term=$22,600
r=rate=1-0.14=
n=number of terms= 5 years
thus the total amount sold will be:
Sn=22600(1-0.14^5)/(1-0.14)
Sn=$26,277.66
The total amount sold was $26,277.66