Question

If in 4 years, at the same rate of interest, the simple interest on ₹3000 is more than the interest on ₹2000 by ₹120. Find the rate of interest.

Answer 1

Let the rate be x% per annum

In first case:
P= $₹3000$
R= $x$%
T= $4$ years
$interest=\frac{P\times T\times R}{100}$
$=\frac{3000\times x\times 4}{100}$
$=₹120x$
$\left[1mark\right]$
In second case:
P= $₹2000$
R= $x$%
T= $4$ years
$interest=\frac{P\times T\times R}{100}$
$=₹\frac{2000\times x\times 4}{100}$
$=₹80x$
$\left[1mark\right]$
According to the statement,
$\Rightarrow 120x-80x=120$
$\Rightarrow 40x=120$
$x=\frac{120}{40}$
$\Rightarrow x=3$
$\therefore$ Rate = $3$%
$\left[1mark\right]$