the cost price of an book is 64 % of the marked price . calculate the gain percent after allowing a discount of 16 % ?
"let marked price = $ 100 . then , c . p . = $ 64 , s . p . = $ 84 gain % = 20 / 64 * 100 = 31.25 % . a"
multiply(subtract(multiply(divide(const_100, 64), divide(subtract(const_100, 16), const_100)), const_1), const_100)