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.

According to the question,

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 Eq. (i) we get

y = 25-10 = 15

Hence, the cost of a pen = Rs. 10

The cost of a pencil box = Rs. 15