Madhya Pradesh Police Exam Model Paper 9

Given:
Rs. 600 become Rs. 720 in 4 years
Concept Used:
Interest = Amount - Principal
If the principal is p, time is t and the rate of interest is r then the simple interest is ptr/100
Calculation:
Rs. 600 become Rs. 720 in 4 years that means
Principal (p) = 600
Amount (A) = 720
Time (t) = 4 year
Let, the rate of interest be r%
Total interest $=720-600$
$\Rightarrow 120$
$\left(600\times 4\times \mathit{r}\right)\}100=120$
$\Rightarrow 24\mathit{r}=120$
$\Rightarrow \mathit{r}=5$
∴ The rate of simple interest per annum is 5%