Small business,

If revenues increase at 18 percent per year, it will take 4.188 years to double. The formula is

T=ln(2)/ln(1+r)

If you ever want to quickly estimate how long it takes for something to double, you can use the Rule of 72. The rule number in this case 72 is divided by the interest number is this case 18. 72 divided by 18 is 4.

## Comments

Just to clarify to the students the difference in the answers this is assuming compounded interest with the original formula : FV=PV(1+r/n)

^{nt}^{ }where t=ln(2)/ln(1+.18) while mine was based on simple interest.