If $10,000 is placed in an investment paying 4.8% yearly interest compounded annually, how long will it take for the account to double?

Answer:
15 years.
Step-by-step explanation:
We have the equation:
20000 = 10000(1 + 0.048)^t where t is the number of years.
1.048 t = 20000/10000 = 2
Taking logs:
t ln 1.048 = ln 2
t = ln 2 / ln 1.048
t = 14.78