On selling 17 balls at Rs. 720, there is a loss equal to the cost price of 5 balls. The cost price of a ball is:

Given Data

• Selling 17 balls yields total SP = Rs. 720
• Loss equals the cost price of 5 balls
• Required: cost price (CP) per ball

Step 1: Express SP and loss in terms of CPLet CP per ball = Rs. cTotal CP for 17 balls = 17cGiven loss = 5c ⇒ SP = CP − loss = 17c − 5c = 12c

Step 2: Equate to the actual SP12c = 720 ⇒ c = 720 ÷ 12 = Rs. 60

Checks & Common Pitfalls

• Loss is given as a multiple of CP, not as a percent; model it directly.
• Do not confuse loss of 5 balls with 5% loss; it is 5 times CP per ball in value.

Final AnswerCost price per ball = Rs. 60.