Question

the price of 5pens and 4pencils is70ruppe the price of 3pens and 7pencils 65ruppes. what is the price of pen.? what is the price of the pencil?​

Answer 1

Given :-

✰ Price of 5 pens and 4 pencils is ₹70

✰ Price of 3 pens and 7 pencils is ₹65

To find :-

☞ Price of pen

☞ Price of pencil

Method :-

Let price of pen be x and price of pencil be y

According to the question,

5x + 4y = 70 → (Equation 1)

3x + 7y = 65 → (Equation 2)

Multiplying Equation 1 by 3 and Equation 2 by 5

3(5x + 4y) = 3(70)

⇒15x + 12y = 210 → (Equation 3)

5(3x + 7y) = 5(65)

⇒15x + 35y = 325 → (Equation 4)

(Equation 4) - (Equation 3)

15x + 35y = 325

(-) 15x + 12y = 210

23y = 115

⇒y = 115 ÷ 23

⇒y = 5

Substitute value of y in any one of the equation

Here, we have Substituted in Equation 1

5x + 4y = 70

⇒5x + 4(5) = 70

⇒5x + 20 = 70

⇒5x = 70 - 20

⇒5x = 50

⇒x = 10

Therefore

• Cost of pen = ₹10
• Cost of pencil = ₹5