
Natalie K. answered 09/27/19
Patient PhD Specializing in Math and Science
According to investopedia, "An ordinary annuity is a series of equal payments made at the end of consecutive periods over a fixed length of time."
Three variables are present when calculating the present value of the ordinary annuity:
r, the interest rate per period
PMT, the period of the cash payment
n, the total number of periods
The equation to calculate the present value is:
Present Value = PMT * ( (1 - (1 + r) - n ) / r )
In this problem, PMT = $150/month, r = 3%/year compounded monthly, and n = 13 years.
The compounding is monthly, so we will convert the years to months:
PMT = $150/month
r = 3%/year = 3% / 1 year * 1 year / 12 months = 0.25% / month = 0.0025 / month
n = 13 years = 13 years * 12 months / 1 year = 156 months
Present Value = 150 * ( ( 1 - (1 + 0.0025)-156 ) / 0.0025 ) = 150 * ( ( 1 - 0.67738647084) / 0.0025) = 150 * 129.045411664 = $19,356.82