On selling 15 balls at Rs. 720, there is a loss equal to the cost price of 5 balls. The cost price of a ball is: Choose one:  A) s. 45  B) s. 50  C) s. 55  D) s. 60  E) s. 72
(C.P. of 15 balls) - (S.P. of 15 balls) = (C.P. of 5 balls)   C.P. of 10 balls = S.P. of 15 balls = Rs.720.   C.P. of 1 ball = Rs.720/10	= Rs. 72.   Answer: Option s. 72
<result>E</result>
On selling 15 balls at Rs. 720, there is a loss equal to the cost price of 5 balls. The cost price of a ball is: