Question: You deposit $P in an account that gives you 8% interest rate per year. If you do not withdraw the money from the account the value of your account keeps growing.

At any given time the value of your money, M, in the account is given by the relationship:

M = P(1+r)^N.
Where, P = initial deposit
r = interest rate = interest rate in percent/100
N = number of years

How long will it take for the initial deposit to double?

Hint: Keep using different values of N to get to the answer