A and B borrowed Rs. 3000 and Rs. 3200 respectively at the same rate of interest for \(2\frac{1 }{2}\) years. If B paid Rs. 40 more interest than A then find the rate of interest per annum.

8%

(Interest paid by B) - (Interest paid by A) = 40

⇒ \(\frac{3200\;×\;R\;×\;5}{2\;×\;100}\) - \(\frac{3000\;×\;R\;×\;5}{2\;×\;100}\) = 40

⇒ \(\frac{200\;×\;R\;×\;5}{2\;×\;100}\) = 40

⇒ R = 8%