on selling 13 balls at rs . 720 , there is a loss equal to the cost price of 5 balls . the cost price of a ball is :
"( c . p . of 13 balls ) - ( s . p . of 13 balls ) = ( c . p . of 5 balls ) c . p . of 8 balls = s . p . of 13 balls = rs . 720 . c . p . of 1 ball = rs . 720 / 8 = rs . 90 . answer : option e"
divide(720, subtract(13, 5))