The Total solution for NCERT class 6-12
The cost of 4 pens and4 pencil boxes is Rs 100. Three times the cost of a pen is Rs 15 more than thecost of a pencil box. Form the pair of linear equations for the abovesituation. Find the cost of a pen and a pencil box.
Solution:
Let the cost of a penand a pencil box be Rs x and Rs y respectively.
According to thequestion,
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 apen = Rs. 10
The cost of a pencilbox = Rs. 15