Question

Rahul spends 85% of his salary and saves Rs.3120 per month. Find his monthly salary.

Answer 1

Hint: To solve this problem we need to first know that how to find the X% of a quantity Y. X% of the Y would be given as $X\%\,of\,Y\,=\dfrac{X}{100}\times Y$. So in this question first we will assume the monthly salary of Rahul equal to a random variable say Rs.X and after that we will calculate the 85% of his salary and then subtract it from the total monthly salary and then will equate it with 3120 to get the value of X. and value of X will be our required answer.

Complete step-by-step answer:
We are given that Rahul spends 85% of his monthly salary and after that his savings per month is Rs.3120, so
To solve this problem, we should know that what is the meaning of percentage,
Y% Percentage is defined as the Y parts per hundred parts of the given quantity.
And Y% of the Z amount is given by = $\dfrac{Y}{100}\times Z$
Now for this question we will first find out the 85% of the monthly salary of the Rahul but before that let us assume the monthly salary of Rahul as Rs.X, so we get
85% of Rs.X as,
$\begin{align}
  & =85\%\,of\,Rs.X \\
 & =\dfrac{85}{100}\times X \\
 & =\dfrac{85}{100}X \\
\end{align}$
Now total savings of Rahul per month will be given by,
$\begin{align}
  & =X-\left( 85\%\,of\,Rs.X \right) \\
 & =X-\dfrac{85}{100}X \\
\end{align}$
Now equating this with the given savings we get,
$\begin{align}
  & X-\dfrac{85}{100}X=3120 \\
 & \Rightarrow \dfrac{15}{100}X=3120 \\
\end{align}$
Cross multiplying we get,
$\begin{align}
  & \Rightarrow X=3120\times \dfrac{100}{15} \\
 & \Rightarrow X=20800 \\
\end{align}$
Hence monthly salary of Rahul we get as, Rs.20800

Note: To solve these kinds of problems you should have prior knowledge of how to calculate the percentage so remember the mentioned formulas in the solution to find percentage. And also some students might just equate the 85% of salary with the savings but it is wrong as it is the savings which we are given in the question so first try to read the question carefully and then solve it.