the side of a square is increased by 40 % then how much % does its area increases ?
"a = 100 a 2 = 10000 a = 140 a 2 = 19600 - - - - - - - - - - - - - - - - 10000 - - - - - - - - - 9600 100 - - - - - - - ? = > 96 % answer : a"
divide(multiply(subtract(square_area(add(const_100, 40)), square_area(const_100)), const_100), square_area(const_100))