解方程~thx

圓球的表面積 = (4π)r²
半圓球的表面積 = (2π)r²

圓柱的表面積 = [(2π)r][2r - 12]

(2π)r² = [(2π)r][2r - 12] = (4π)r² - (24π)r

(2π)r² = (4π)r² - (24π)r

24r = 2r²

r = 12 cm

圓球的體積 = (4π/3)r³
半圓球的體積 = (2π/3)r³ = (2π/3)(12)³ = 1152π cm³

圓柱的體積 = (πr²)(2r - 12) = (144π)(12) = 1728π cm³

總體積 = 2880 cm³