At what rate percent of simple interest will a sum of money double itself in 20 years?
4%
5%
6%
8%
Explanation:
Let sum = x
Time = 20 years
Simple Interest = x
$\text{R = }\dfrac{100 \times \text{SI}}{\text{PT}} = \dfrac{100 \times x}{x \times 20} = \dfrac{100}{20} = 5\%$