On selling 9 balls at Rs. 720, there is a loss equal to the cost price of 5 balls. The cost price of a ball is: Choose the correct choice from the following answers:  A) s. 145  B) s. 150  C) s. 155  D) s. 160  E) s. 180
(C.P. of 9 balls) - (S.P. of 9 balls) = (C.P. of 5 balls)   C.P. of 4 balls = S.P. of 9 balls = Rs.720.   C.P. of 1 ball = Rs.720/4	= Rs. 180.   Answer: Option s. 180
<result>E</result>
On selling 9 balls at Rs. 720, there is a loss equal to the cost price of 5 balls. The cost price of a ball is: