Question

The least number of complete years in which a sum of money put out at 20% compound ineterst will be more than doubled is:

Answer 1

$\begin{aligned} P(1+\frac{R}{100})^n > 2P \\ (1+\frac{20}{100})^n > 2 \\ (\frac{6}{5})^n > 2 \\ \frac{6}{5} \times \frac{6}{5} \times \frac{6}{5}\times\frac{6}{5} > 2 \end{aligned}$

So answer is 4 years