if the cost price of 12 pencils is equal to the selling price of 8 pencils , the gain percent is :
c 50 % let c . p . of each pencil be $ 1 . then , c . p . of 8 pencils = $ 8 ; s . p . of 8 pencils = $ 12 . gain % = 4 / 8 * 100 = 50 %
divide(const_100, divide(8, subtract(12, 8)))