EX.2.2 Q13 Linear Equations in One Variable Solutions - NCERT Maths Class 8


A rational number is such that when you multiply it by \(\begin{align}\frac{5}{2}\end{align}\) and add \(\begin{align}\frac{2}{3}\end{align}\)to the product, you get \(\begin{align}\frac{-7}{12}\end{align}\). What is the number?

 Video Solution
Linear Equations
Ex 2.2 | Question 13

Text Solution

What is known?

A rational number is such that when multiply it by\(\begin{align}\frac{5}{2}\end{align}\) and add\(\begin{align}\frac{2}{3}\end{align}\)  to the product, answer is \(\begin{align}\frac{-7}{12}\end{align}\).

What is unknown?



Assume the rational number to be a variable. Apply the conditions sequentially to form a linear equation.


Let the rational number be \(x\)

Multiply by \(\begin{align}\frac{5}{2} \to x \times \frac{5}{2} = \frac{{5x}}{2}\end{align}\)

Add  \(\begin{align}\frac{2}{3}\end{align}\)in the product  \(\begin{align}= \frac{{5x}}{2} + \frac{2}{3}\end{align}\)

Answer is \(\begin{align}➔ \frac{{ - 7}}{{12}}\end{align}\)

\[\begin{align} \therefore \quad \frac{{5x}}{2} + \frac{2}{3} &= \frac{{ - 7}}{{12}}\\\frac{{5x}}{2} &= \frac{{ - 7}}{{12}} - \frac{2}{3}\\\frac{{5x}}{2} &= \frac{{ - 7 - 8}}{{12}}\\\frac{{5x}}{2} &= \frac{{ - 15}}{{12}}\\x &= \frac{{ - 15}}{{12}} \times \frac{2}{5}\\x &= \frac{{ - 3}}{6}\\x &= \frac{{ - 1}}{2}\end{align}\]

The number is  \(\begin{align}- \frac{1}{2}.\end{align}\)

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