Question

Sandeep borrowed $\text{Rs.}3000$ for $4$ years and $\text{Rs.}8000$ for $2\frac{1}{2}$ years from Sonia at the same rate of interest. The total interest earned by Sonia is $\text{Rs.}2880$. Find the rate of interest.

Answer 1

Let the rate of interest be equal to $r$.

As we know that,

$\text{Simple interest}=\frac{\text{Principle}\times \text{rate}\times \text{time}}{100}$

By using the above formula and given information that the total interest is equal to $\text{Rs.}2880,$

$\begin{array}{cc}\text{Total interest}& =\frac{3000\times r\times 4}{100}+\frac{8000\times r\times \frac{5}{2}}{100}\\ 2880& =120r+200r\\ 320r& =2880\\ r& =\frac{2880}{320}\\ r& =9\%\end{array}$