if the radius of a circle is decreased 20 % , what happens to the area ?
"area of square = pi * radius ^ 2 new radius = 4 / 5 * old radius so new area = ( 4 / 5 ) ^ 2 old area = > 16 / 25 of old area = > 64 % old area answer : c"
subtract(const_100, multiply(power(divide(20, const_100), const_2), const_100))