Question

Mr Garg lent Rs.15000 to his friend. He charged 15% per annum on Rs.12500 and 18% on the rest. How much interest does he earn in 3 years?

Answer 1

Hint: To solve this problem we need to know that how to calculate interest in the T years, for that we have a direct formula $=\dfrac{P\times R\times T}{100}$ where P is the principal amount and R is the rate of interest.
So in the given question we will apply the above mentioned formula on Rs.12500 and the same formula on the rest of the amount with different rates of interest. And after that we will add both the interests to get the answer.

Complete step-by-step answer:
We are given that Mr Garg lent Rs.15000 out of which he charged 15% interest on Rs.12500 and 18% on the rest so first we have to that how can we calculate interest on the principle amount P for T years at the interest rate R, it can be calculated as,
$=\dfrac{P\times R\times T}{100}$
So out of Rs15000,
15% rate of interest is applied on Rs.12500 so we get interest on Rs.12500 as,
$=\dfrac{P\times R\times T}{100}$
Putting P = 12500, R = 15 and T = 3, we get
\[\begin{align}
  & =\dfrac{12500\times 15\times 3}{100} \\
 & =125\times 15\times 3 \\
 & =5625 \\
\end{align}\]
Rest of the amount we get as,
= 15000 – 12500 = Rs.2500
And rate of interest on it is 18%,
So total interest on Rs2500 for 3 years we get as,
$=\dfrac{P\times R\times T}{100}$
Putting P = 2500, R = 18 and T = 3, we get
$=\dfrac{P\times R\times T}{100}$
\[\begin{align}
  & =\dfrac{2500\times 18\times 3}{100} \\
 & =25\times 18\times 3 \\
 & =1350 \\
\end{align}\]
So total interest that Mr Garg earned in 3 years is,
$=5625+1350=Rs.6975$
Hence we get our answer as Rs.6975

Note: You need to be careful while solving this question some students may just calculate the 15% interest on the entire amount and may not calculate interest on both amounts differently so be careful about that. And also remember the formula for the interest as $\dfrac{P\times R\times T}{100}$ for the future problems.