the area of a circle is increased by 800 % . by what percent has the radius of the circle increased ?
"the area of the circle is increased by 800 % , thus the area is increased 9 times . the area of a circle it proportional to the square of the radius ( area = π r ^ 2 ) , therefore the radius must increase 3 times ( diameter increase 3 times = area increase 9 times ) , which is increase by 200 % . answer : e ."
multiply(const_100, divide(const_2, const_2))