Question

roberta deposited 4,790.23 into a saving account with an interest rate of 3.8% compunded twice a year. about how long will it takefor the account to be worth 9,000?

Answer 1

4009 is the answer I got

Answer 2

The answer to this question would be: 17 years
The interest rate is 3.8% compounded twice a year. The function of the saving account amount would be:
f(x)= 4,790.23* (1+ 0.038/2)^2x
f(x)= 4,790.23* (1.019)^2x

Then for f(x)= 9,000 the x value would be:
9,000= 4,790.23* (1.019)^2x
9,000/4,790.23= (1.019)^2x
1.8788= (1.019)^2x
2x=34
x=17