Ex.4.1 Q1 Linear Equations in Two Variables Solution - NCERT Maths Class 9
The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement. (Take the cost of a notebook to be \(₹\, x\) and that of a pen to be \(₹\, y.\))
- Let the cost of one notebook be \(₹\, x\)
- Let the cost of one pen be \(₹\, y\)
Given: Cost of notebook is twice the cost of pen.
Therefore, we can write the required linear equation in two variables considering the given information as,
Cost of notebook \(= 2 \times\) Cost of pen
\(\Rightarrow x = 2 y\)
Since any linear equation of two variables is expressed as:
\(a x + b y + c = 0,\)
\(\therefore \,x - 2 y = 0\) is the required linear equation in two variables which represents the given information.