Question

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

• A. $3$
• B. $4$
• C. $5$
• D. $6$

Answer 1

The correct option is B $4$

$P{(1+\frac{20}{100})}^n>2P\Rightarrow {\left(\frac{6}{5}\right)}^n>2$.
Now, $(\frac{6}{5}\times \frac{6}{5}\times \frac{6}{5}\times \frac{6}{5})>2$.
So, $n=4years$.