Question

If you earn an annual interest rate of 10.3 percent, how many years will it take to quadruple your money?

14.14 years

13.05 years

12.86 years

11.31 years

12.37 years

Answer 1

We use the formula:
A=P(1+r/100)^n
where
A=future value($4x)
P=present value($x say)
r=rate of interest
n=time period.

4x=x*(1.103)^n

4=(1.103)^n

Taking log on both sides;

log 4=n*log (1.103)

n=log 4/log (1.103)

=14.14 years(Approx).