Vipul invests a sum of Rs. 5400 and Vijay invests a sum of Rs. 9400 at the same rate of simple interest per annum. If, at the end of 4 years, Vijay gets Rs. 840 more interest than Vipul, then find the rate of interest per annum (in percentage).

Correct option is D

Given:

Vipul's principal = ₹5400

Vijay's principal = ₹9400

Time = 4 years (same for both)

Difference in interest = ₹840

We are to find the rate of interest per annum (R%).

Formula Used:

SI = $$\frac{P \times R \times T}{100}$$​​

Solution:

SI(Vijay) – SI(Vipul) = 840

​$$\frac{9400 \times R \times 4}{100} - \frac{5400 \times R \times 4}{100} = 840 \\ \ \\frac{(9400 - 5400) \times R \times 4}{100} = 840 \\ \ \\\frac{4000 \times R \times 4}{100} = 840\\ \ \\\frac{16000R}{100} = 840\\ \ \\160R = 840 \\ \ \\R = \frac{840}{160} = 5.25 \%$$​​