Keshav invests a sum of Rs. 5400 and Tushar invests a sum of Rs. 10200 at the same rate of simple interest per annum. If, at the end of 3 years, Tushar gets Rs. 360 more interest than Keshav, then find the rate of interest per annum (in percentage).

Correct option is C

Given:

Keshav's investment = Rs. 5400
Tushar's investment = Rs. 10200
Time period for both = 3 years
The difference in interest = Rs. 360
Formula Used:
​$$\text{Simple Interest (SI)} = \frac{P \times R \times T}{100}$$​​
where,
P = Principal,
R = Rate of interest,
T = Time in years.
Solution:
Let the rate of interest per annum be R%.
Interest for Keshav = $$\frac{5400 \times R \times 3}{100} = \frac{16200\times R}{100} = 162R$$​​

Interest for Tushar = $$\frac{10200 \times R \times 3}{100} = \frac{30600 \times R}{100} = 306R$$​​
The difference in interest = Interest for Tushar - Interest for Keshav
306R - 162R = 360
144R = 360
R = $$\frac{360}{144}$$ = 2.5
Thus, the rate of interest per annum is 2.5%.