Question 269225
Kimberly invested $7000 in her savings account for 4 years. When she withdrew it, she had $7705.31. Interest was compounded continuously. What was the interest rate on the account? 

The formula for compound continuous interest is:

A = P*e^(rt)

In this case A = 7705.31, P = 7000, and t = 4 so:

7705.31 = 7000*e^(4r)

e^(4r) = 7705.31/7000

Taking the natural log of both sides above we get:

Ln (e^(4r)) = Ln (7705.31/7000)

Using the fact that Ln (e^a) = a the left side becomes: 

4r = Ln(7705.31/7000)
r = [Ln(7705.31/7000)]/4

Use natural log tables and calculate r.