math
posted by marie .
find the interest rounded to the nearest dollar
periodic deposit
$60 at the end of each month
Rate
5% compounded monthly
Time
30 years

I assume 5% is annual interest compounded monthly.
Use the compound interest formula:
Future value
=P((1+r)^n1)/r
where
P=monthly payment, =$60
r=interest rate per period = .05/12
n=number of periods = 30*12
then
Future value
=60*((1+0.05/12)^3601)/(0.05/12)
=49935.52
From the future value, subtract the total of monthly payments over 360 months at $60 per month to get the interest.