Chetan invests a sum of Rs. 5400 and Vipul invests a sum of Rs. 10200 at the same rate of simple interest per annum. If, at the end of 3 years, Vipul gets Rs. 720 more interest than Chetan, then find the rate of interest per annum (in percentage).

Correct option is C

Given:

Chetan's principal (P₁) = ₹5400

Vipul's principal (P₂) = ₹10200

Time (T) = 3 years (same for both)

Difference in interest = ₹720

Need to find: Rate of interest per annum (R%)

Formula Used:

Use Simple Interest (SI) formula:

SI = $$\frac{P × R × T}{100}$$​​

Solution:

​$$\text{SI}_{\text{Vipul}} - \text{SI}_{\text{Chetan}} = \frac{P_2 × R ×T}{100} - \frac{P_1 × R × T}{100}$$​​

​$$= \frac{(P_2 - P_1) × R × T}{100}$$​​

Now, 

​$$720 = \frac{(10200 - 5400) × R × 3}{100} \\ \ \\ 720 = \frac{4800 × R × 3}{100} \\ \ \\720 = \frac{14400R}{100} \\ \ \\720 = 144R \\ \ \\R = \frac{720}{144} = 5 \%$$​​