# NCERT Class 9 Solution: Linear Equation In Two Variables (Chapter 4) Exercise 4.1

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Q-1 The cost of a notebook is twice the cost of a pen. Write a linear equation in two variable to represent this statement.

(Take the cost of a notebook to be Rs and that of a pen to be Rs )

Solution:

Consider the cost of a notebook be and that of a pen be .

A linear equation has to equate the two things. According to question, the cost of a notebook is twice the cost of a pen

So,

Therefore, linear equation becomes,

.

Q-2 Express the following linear equations in the form and indicate the value of in each case:

i.

ii.

iii.

iv.

v.

vi.

vii.

viii.

Solution:

i.

So,

Compare, the equation with

Therefore, value of and is

ii.

Compare the equation with .

Therefore, .

iii.

So,

Compare, the equation with

Therefore,

iv.

So,

Compare, the equation with

Therefore,

v.

So,

Compare, the equation with

Therefore,

vi.

Compare, the equation with

Therefore,

vii.

Compare, the equation with

Therefore,

viii.

So,

Compare, the equation of

Therefore,