Derek invests $250 per month for years at 4.8%/a compounded monthly.

Question

How much will his investment be worth at the end of the years?

Answer 1

at the end of how many years ????

amount = 250 (1.004^(number of months) - 1)/.004

Answer 2

you can use the annuity formula for future value:
FV=R((1+i)^n-1)/(i)

R=250
i=4.8%/12
n=12*number of years
find the FV