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?

FV =PV x [1 + R]^N

20,000 = 10,000 x [1 + 0.048]^N, solve for N

Divide both sides by 10,000

2 = 1.048^N

N =Log(2) / Log(1.048)

N =~ 14.78 years for $10,000 to become $20,000.