Mukund invests a sum of Rs. 5400 and Sachin invests a sum of Rs. 9400 at the same rate of simple interest per annum. If, at the end of 5 years, Sachin gets Rs. 960 more interest than Mukund, then find the rate of interest per annum (in percentage).

Correct option is D

​Given:
​​Principal of Mukund (P₁) = Rs. 5400
​​Principal of Sachin (P₂) = Rs. 9400
​​Time (T) = 5 years
​​Difference in Interest = Rs. 960
​​Formula Used:
​​Simple Interest (SI) = (P × R × T) / 100
​​Solution:
​​Let the rate of interest be R%.
​​Interest by Sachin - Interest by Mukund = Rs. 960
​​​$$\Rightarrow \frac{9400 \times R \times 5}{100} - \frac{5400 \times R \times 5}{100} = 960\\\Rightarrow \left( \frac{R \times 5}{100} \right) \times (9400 - 5400) = 960\\\Rightarrow \left( \frac{R \times 5}{100} \right) \times 4000 = 960\\\Rightarrow \frac{R \times 20000}{100} = 960\\\Rightarrow 200R = 960\\\Rightarrow R = \frac{960}{200} = 4.8\%$$​​​​
​​Therefore, the rate of interest per annum is 4.8%.​