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 ₹)?

33 45 30 22

30

On selling 18 pens at 660, there is a profit equal to the cost price of 4 pens. 18(sp - cp) = 4cp 9(sp - cp) = 2cp 9sp - 9cp = 2cp 9sp = 11cp … (1) As we know that selling price of 18 pens is 660. 18sp = 660 3sp = 110 …. (2) Put Eq.(2) in Eq.(1). 3 ×110 = 11cp CP = 30