NCERT Solutions
Class 9 - Mathematics - Chapter 4: LINEAR EQUATIONS IN TWO VARIABLES - EXERCISE 4.1
Question 1

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Question. 1

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.)

Answer:

x − 2y = 0

Detailed Answer with Explanation:

Let notebook cost be \(x\) and pen cost be \(y\). The statement says notebook cost is twice pen cost, so \(x = 2y\).

Move all terms to one side to match \(ax + by + c = 0\): \(x - 2y = 0\).

This is linear because the highest power of \(x\) and \(y\) is 1.