Question

A man buys 5 pens and 30 books for rs. 1000. He sells pens at a profit of 15% and books with a gain of 10% . If his overall gain is rs. 120 , the CP of the pen is?

Answer 1

Cost price of the pen is Rs. 80.

• Let the cost price of 5 pens be x and cost price of 30 books be y.
• Now according to the given condition, x + y = 1000
• After selling pens he earns a profit of 15% , therefore selling price of the pens will be (0.15x + x) = 1.15x

• After selling books he earns a profit of 10% , therefore selling price of the books will be (0.1y + y) = 1.1y
• Overall gain is Rs. 120, therefore total money he has after selling = cost price + profit = 1000 + 120 = 1120
• Now the selling price equation becomes - 1.15x + 1.1y = 1120
• Now soling the two equations we have -

x + y = 1000

1.15x + 1.1y = 1120

we get the solution as x = 400 and y = 600

• Now we need to find the cost price of the pen so we need to divide 'x'  by 5 as we considered the cost price of 5 pens to be 'x'
• After dividing the x by 5 we get the cost price of the pen is Rs. 80.