题解 | #球的表面积#

import math


class BallArea:
    def __init__(self, r):
        self.r = r

    def Area(self, r):
        s = 4 * math.pi * pow(r, 2)
        return s


for i in [1, 2, 4, 9, 10, 13]:
    b = BallArea(i)
    print(round(b.Area(i), 2))