SOLUTION: Need help with this. Thanks! A woman deposits $50,000 in a savings account with 4% continuously compound interest. How many years must she wait until the balance has doubled?

If you need immediate math help from PAID TUTORS right now, click here. (paid link)
Click here to see ALL problems on Exponential-and-logarithmic-functions

Question 140090: Need help with this. Thanks!
A woman deposits $50,000 in a savings account with 4% continuously compound interest. How many years must she wait until the balance has doubled?
Answer by scott8148(5896) (Show Source):
You can put this solution on YOUR website!
the formula you need is A=Pe^(rt)
__ A is the Amount after time t
__ P is the Principal you start with
__ e is Euler's number (the base for natural logarithms)
__ r is the rate of interest
__ r and t have to use the same time units

100000=50000e^(.04t) __ dividing by 50000 __ 2=e^(.04t)

taking natural log __ ln(2)=.04t __ dividing by .04 __ [ln(2)]/.04=t