If the simple interest on a certain sum of money for 4 years is one–fifth of the sum, then the rate of interest per annum is
4%
7%
6%
5%
Explanation:
Let the Principal [P] be x
Then, Simple Interest [SI] = x/5
Time [T] = 4 years
$\text{Rate of interest per annum(R) = }\dfrac{100 \times \text{SI}}{\text{PT}} = \dfrac{100 \times \dfrac{x}{5}}{x \times 4} = \dfrac{20}{4}= 5\%$