Question

P and Q invest Rs. 36,000 and Rs. 25,000 respectively at the same rate of interest per year. If at the end of 4 years, P gets Rs. 3,080 more interest than Q, find the rate of interest.

Answer 1

P's investment (P₁) = Rs. 36000

and Q's investment (P₂) = Rs. 25000

Period (T) = 4 years, Let rate of interest = x%

P's interest = Rs. `(36000 xx "x" xx 4)/100`

= Rs. 1440x    `(∵ "S.I." = "PRT"/100)`

and Q's interest =`(25000 xx "x" xx 4)/100` = Rs. 1000x

Difference in their interest

= Rs. (1440 - 1000)x = Rs. 440x

But the difference = Rs. 3080

∴ 440x = 3080 ⇒ x = `3080/440` ⇒ x = 7%

∴ Rate of interest = 7% p.a.