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  • The cost of 4 pens and 4 pencil boxes is Rs 100. Three times the cost of a pen is Rs 15 more than the cost of a pencil box. Form the pair of linear equations for the above situation. Find the cost of a pen and a pencil box.

The cost of 4 pens and 4 pencil boxes is Rs 100. Three times the cost of a pen is Rs 15 more than the cost of a pencil box. Form the pair of linear equations for the above situation. Find the cost of a pen and a pencil box.

Answers (1)

Solution:
Let the cost of a pen is x and the cost of a pencil box is y.
As per the question
4x + 4y = 100 … (1)
3x = y + 15 … (2)
Divide equation (1) by 4.
x + y = 25    ………..(3)
By adding equation (1) and (3) we get
4x = 40
x = 10
Put x = 10 in eq. (1)
40 + 4y = 100
4y = 100 – 40
y = 60/4 = 15
x = 10, y = 15
Cost of pen = Rs. 10
Cost of pencil box = Rs.15

 

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