Question

7 pens and 3 pencils together cost Rs50, while 3 pens and 7 pencils
together cost Rs 30. The cost of a pen and that of a pencil​

Answer 1

✰︎✪︎ AnswEr ✪︎✰︎

pen = ₹ 6.5 ; pencil = ₹ 1.5

✞︎ Given :-

• 7 pen and 3 pencils together cost ₹50
• 3 pens and 7 pencils together cost ₹30

❦︎ To find :-

• The cost of a pen and that of a pencil

✯︎ Solution :-

Let pen be x

and , pencil be y

According to Question ,

➪︎ 7x + 3y = 50......(1)

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And also ,

➪︎ 3x + 7y = 30.....(2)

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Multiply 3 to (1) & 7 to (2),

➪︎ 21x + 9y = 150

➪︎ 21x + 49y = 210 [ here signs will change ]

(-) (-) (-)

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- 40y = - 60

40y = 60

➪︎ y = 60/40 = 3/2

✰︎ y = 3/2

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Substitute y value in (1)

➪︎ 7x + 3(3/2) = 50

➪︎ 7x + 9/2 = 50

➪︎ 14x + 9 /2 = 50

➪︎ 14x + 9 = 100 (50 × 2)

➪︎ 14x = 100 - 9

➪︎ 14x = 91

➪︎ x = 91/14

✰︎ x = 13/2

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Therefore ,

• Cost of pen = 13/2 = ₹ 6.5
• Cost of pencil = 3/2 = ₹ 1.5