Question

A conservationist determines that a particular beach is eroding at a rate of 1.1% each year. When writing an explicit formula to represent the amount of beach remaining each year, which value should she use as the common ratio?

0.011
0.089
0.989
1.011

Answer 1

0.989

Since the beach loses 1.1% per year, the remaining fraction each year is 1 − 0.011 = 0.989, so A_n = A_0*(0.989)^n.