Question

Siri bought 2 notebooks and 3 pens for Rs 90 . Lakshmi bought

4 notebooks and 5 pens for Rs 140. Form linear equations for the given

situation to find the cost of a pen and a notebook .​

Answer 1

Answer:

3 Pen +4 Notebook =110 rupees

Multiply by 5,

15 Pen +20 Notebook  =550 rupees

7 Pen +5 Notebooks   =170 rupees

Multiply by 4,

28 Pen +20 Notebook  =680 rupees

15 Pen +20 Notebook  =550 rupees

Equating and solving for Pen,

Cancelling notebook,

13 Pen  =130 Hence,

Pen  =10 rupees

Substituting,

3(10)+4 Notebook =110

4 Notebook =110−30 Hence,

Notebook =20 rupees

Answer 2

Given :- Siri bought 2 notebooks and 3 pens for Rs 90 . Lakshmi bought 4 notebooks and 5 pens for Rs 140. Form linear equations for the given situation to find the cost of a pen and a notebook .

Solution :-

Let us assume that, cost of a notebook is x and a pen is y .

so,

→ 2x + 3y = 90 -------- Eqn.(1)

→ 4x + 5y = 140 ------- Eqn.(2)

Eqn.(1) and Eqn.(2) are required linear equations .

multiply Eqn.(1) by 2 and subtracting Eqn.(2) from result,

→ 2(2x + 3y) - (4x + 5y) = 2*90 - 140

→ 4x - 4x + 6y - 5y = 180 - 140

→ y = 40 .

putting value of y in Eqn.(1)

→ 2x + 3*40 = 90

→ 2x = 90 - 120

→ 2x = (-30)

→ x = (-15)

since value of x is negative , given data is not correct.

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