The cost of 4 pens and 4 pencil boxes is rs100. Three times the coat of a pen is rs 15 more than the cost of pencil box. Form the paid of linear equations for the above situation. Find the cost of a pen and pencil box
Answers
Answer:
Let the cost of a pen be Rs 'x' and the cost of a pencil box be Rs. 'y'
As, the cost of 4 pens and 4 pencil boxes is Rs. 100
So, 4x + 4y = 100 .................(1)
And, three times the cost of a pen is Rs. 15 more than the cost of a pencil box.
So, 3x = y + 15
⇒ 3x - y = 15 ......................(2)
Now multiplying the equation (1) by 3 and equation (2) by 4, we get
⇒ (4x + 4y = 100)*(3) = 12x + 12y = 300 ................(3)
⇒ (3x - y = 15)*(4) = 12x - 4y = 60 ..........................(4)
Now, subtracting (4) from (3)
12x + 12y = 300
12x - 4y = 60
- + -
_________________
16y = 240
_________________
⇒ 16y = 240
⇒ y = 240/16
⇒ y = 15
Now, substituting the value of y = 15 in (2)
⇒ 3x - y = 15
⇒ 3x - 15 = 15
⇒ 3x = 15 + 15
⇒ 3x = 30
⇒ x = 30/3
⇒ x = 10
So, the cost of a pen is Rs. 10 and the cost of a pencil box is Rs. 15
Answer.
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