Question

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.

Answer 1

Let the cost of a pen and a pencil box be Rs x and Rs y respectively.

4x + 4y = 100

Or x + y = 25   ......(i)

3x = y + 15

Or 3x – y = 15   ......(ii)

On adding equation (i) and (ii), we get

4x = 40

So, x = 10

Substituting x = 10 in equation (i), we get

y = 25 – 10 = 15

Hence, the cost of a pen = Rs.10

The cost of a pencil box = Rs.15