Question 1030624: If Angela has $500 to invest at %2.5 per annum compounded quarterly, how long will it be before she has $750? Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! 750=500*{1+0.025/4)^4k
1.5=(1.00625)^4k
take ln of both sides
0.4055=4k ln (1.00625)=4k*0.00623
do without rounding
ln(1.5)/4*ln1.00625
k=16.27 years
Does this make sense?
Money doubles with 72/interest rate, which here would be about 28.8 years. This is reasonable. It can be shown with compounding that increasing 50% is roughly 40/interest rate, which here would be 16 years.
