Question

A invests $₹8,000$ and $B$ invests $₹11,000$ at the same rate of interest per annum. If at the end of 3 years, $B$ gets $₹720$ more interest than $A$; find the rate of interest.

Answer 1

Let the rate of interest $=R\%$ per annum.
For $A:P=₹8,000$ and $T=3$ years
$$\therefore I=\frac{₹8,000\times R\times 3}{100}=₹240R[\because I=\frac{P\times R\times T}{100}]\left(1Mark\right)$$
For $B:P=₹11,000$ and $T=3$ Years
$\therefore I=\frac{₹11,000\times R\times 3}{100}=₹330R$( 1 Mark)
$\therefore 330R-240R=720[\because B$ gets $₹720$ more interest than $A]$
$\Rightarrow 90R=720$ and $R=\frac{720}{90}=8$
$\Rightarrow$ Rate of interest $=8\%$(1 Mark)