Problem: if the radius of a circle is decreased 50 % , what happens to the area ?
Rationale: "area of square = pi * radius ^ 2 new radius = 0.5 * old radius so new area = ( 0.5 ) ^ 2 old area = > 0.25 of old area = > 25 % old area ans : c"
annotated_formula: subtract(const_100, multiply(power(divide(50, const_100), const_2), const_100))