Amit invests a sum of ₹5400 and Gopal invests a sum of ₹9400 at the same rate of simple interest per annum. If, at the end of 3 years, Gopal gets ₹840 more interest than Amit, then find the rate of interest per annum (in percentage).

Correct option is B

Given:

Amit invests ₹5400 and Gopal invests ₹9400 at the same rate of simple interest per annum.

At the end of 3 years, Gopal gets ₹840 more interest than Amit.

Formula Used:

Simple Interest (SI) = $$\frac{(Principal × Rate × Time) }{ 100}$$​​

Interest difference = SI of Gopal - SI of Amit 

Difference in Principal  $$= P_G - P_A$$​​

Interest difference  = $$I_D$$​​

Time  = t

​$$\Rightarrow \quad \frac{I_D \times 100}{t \times (P_G - P_A)}$$​​
​

Solution:​

​$$R = \frac{₹840 \times 100}{3 \times (₹9400 - ₹5400)} \\[6pt]R = \frac{84000}{3 \times 4000} \\[6pt]R = \frac{84000}{12000} \\[6pt]R = 7 \%$$​​