Question

一圆柱底面周长20cm,高与半径的和是15cm,求表面积.【急!】

Answer 1

底周长=2*pi*R = 20,所以 R = 10/pi

h + R = 15 => h = 15 - 10/pi

S = [2 * pi * R^2] + 20 * h = 2 * pi * 10 * 10 / pi^2 + 20(15-10/pi) = 200 / pi + 300 - 200 / pi = 300 平方厘米