On selling 18 pens at ₹660, there is a profit equal to the cost price of 4 pens. What is the cost price of one pen (in ₹)?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 30
Let's assume the cost price and selling price of each pen are 'cp' and 'sp'.
On selling 18 pens at 660, there is a profit equal to the cost price of 4 pens.
Profit = sp - cp
⇒ 18 (sp - cp)
⇒ 9 (sp - cp)
⇒ 9sp - 9cp = 2cp
⇒ 9sp = 2cp + 9cp
⇒ 9sp = 11cp ....Eq (i)
As we know the selling price of 18 pens is 660.
⇒ 18sp = 660
⇒ 3sp = 110 ....Eq.(ii)
Put Eq.(ii) in Eq.(i).
⇒ 3 × 110 = 11cp
⇒ cp = 30
So the cost price of one pen = 30