Question

The cost of 4 pens and 4 pencil boxes is ₹100 . Three times the cost of a pen is ₹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.

Answer 1

Let the cost of 1 pen be ₹x and that of 1 pencil box be ₹y.
Now,
Cost of 4 pens + Cost of 4 pencil boxes = ₹100 (Given)
⇒ 4x + 4y = 100
⇒ x + y = 25 .....(i)
Also,
3 × Cost of a pen = Cost of a pencil box + ₹15
3x = y + 15
⇒ 3x − y = 15 .....(ii)
Adding (i) and (ii), we get
4x = 40
⇒ x = 10
Putting x = 10 in (i), we get
10 + y = 25
⇒ y = 15
Thus, the cost of a pen = ₹10 and that of a pencil box = ₹15.