
Lenny D. answered 01/17/20
Financial Professional with many years of Wall Street Experience
Let’s start with some definitions
The Present value PV, of a stream of payments, A for T periods discounted at some rate,
I, is given as PV=A*K(I,T) where K is a multiplier which increases as the number of periods increases and decreases as the interest rate increases. Formally,
K=(1/i)(1-(1/(1+i)T) = (1/i)(1/(1+i)T)((1+i)T-1) where I is the PERIODIC INTEREST RATE and T is the NUMBER of PERIODS So for a thirty year mortgage with a 12% rate we would have 360 monthly payments with a rate of 6%/15 or 0.5% monthly rate.
In your case A= 405 i=3.75%/2 T= 24 semi annual payments.
So K = (1/.01875)(1-(1/(1.01875))24) =(1/.01875)(.35971)= 19.1845 os 1 dollar for every 6 months for the next 12 years is worth about 19.18 in PV so,
405*k = 7,769.72 dollars. That is the fair price of your annuity
Hope this helps
Lenny D.
Your formula is for the present value of 405 dollars to be received 24 periods in the Future (1/((1.01875)^24) is <1. That is the 24 period discount factor for a single cash flow.01/19/20