# NCERT Class 9 Solution: Linear Equation in Two Variables (Chapter 4) Exercise 4.1 (For CBSE, ICSE, IAS, NET, NRA 2022)

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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 ₹ and that of a pen to be ₹ )

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,