Mohan invests a sum of Rs. 5400, and Varun invests a sum of Rs. 9400 at the same rate of simple interest per annum. If, at the end of 6 years, Varun gets Rs. 480 more interest than Mohan, then find the rate of interest per annum (in percentage).

Correct option is D

Given:
Principal of Mohan = Rs. 5400
Principal of Varun = Rs. 9400
Time = 6 years
Difference in interest = Rs. 480
Formula Used:
Simple Interest (SI) = $$\frac {P × R × T}{100}$$​​
Solution:
Let the rate of interest be R% per annum.
Interest received by Mohan:
​$$SI_{Mohan} = \frac{5400 \times R \times 6}{100}$$​​
Interest received by Varun:
​$$SI_{Varun} = \frac{9400 \times R \times 6}{100}$$​​
According to the question:
​$$\frac{9400 \times R \times 6}{100} - \frac{5400 \times R \times 6}{100} = 480\\ \ \\ \frac{(9400 - 5400) \times R \times 6}{100} = 480\\ \ \\ \frac{4000 \times R \times 6}{100} = 480\\ \ \\ \frac{24000R}{100} = 480\\ \ \\ 240R = 480\\ \ \\ R = \frac{480}{240} = 2\%$$​​