They made a mistake. According to their formula, your answer is correct.
Going off this site
The Present Value and Future Value of an Annuity; Annuity Due, Ordinary Annuity; Time Value, with Formulas and Examples; Discount Rate
I am trying to figure out how annuities and interest works.
So I decided to Calculate this:
100 * ((1+.005)120 -1)/.005
A * (1 + i)n - 1 / i
n= number of periods
According to the website the answer is $36,387.93
But when I put it in on my calculator, the answer is $16,387.93
My answer is exactly $20,000 less than the answer the site gives.
Any reason for this?