AP Calc help......>!<?

Question

a bank account earns interest compounded continuosly at a rate of 6% per year how long will it take approximately for the account to triple in value
a. 3yrs
b. 9yrs
c. 18 yrs
d. 33 yrs
e. 50yrs

Answer 1

Compounded continuously means A = P * e^(rt)

3P = P [e^(.06t)] ===> 3 = e^(.06t)
ln 3 = .06 t
t = ln3 / .06
t approx = 18.31

c.

Answer 2

A(1+i)^n=3A

(1+0.06)^n=3
nlog(1,06)=log3
n=log3/log1,06
=0,4771/0,0253
=18 years