Question

help please
When he was 40, Keefer began investing $150 per month in various securities for his retirement savings. His investments averaged a 4.5% annual rate of return until he retired at age 70. What was the value of Keefer’s retirement savings when he retired? Assume monthly compounding of interest.

Answer 1

@sarah786

Answer 2

@hartnn

Answer 3

No idea. I'm not a maths helper :/

Answer 4

@dumbcow

Answer 5

you need to use a future value equation involving a geometric series
\[FV = 150( r +r^2 +...r^{360})\]
where
\[r = 1 + \frac{.045}{12}\]
The sum of geometric series is:
\[FV = \frac{150r(r^{360} - 1)}{r - 1}\]
here is calculation:
http://www.wolframalpha.com/input/?i=150r%28r%5E360+-1%29%2F%28r-1%29%2C+r+%3D+1%2B%28.045%2F12%29