簡單球體面積及體積問題！

下列各題r为半徑 6. 4πr^2=6(10)(10)
r=6.91cm7.4π(6)^2+4π(8)^2=4πr^2
4π(6^2+8^2)=4πr^2
r=10cm8a.表面面積之比=4π6380^2 : 4π1750^2
=13.3:1
8b.體積之比=(4/3)π6380^3:(4/3)π1750^3
=48.5:19.(4/3)π1^3 × 8 = (4/3)πr^3
r=2 cm
直徑=2×2
=4 cm10.體積=(4/3)π9^3-(4/3)π8^3
=909cm^311.設原來水位是h cm
(4/3)πr^3 + π(64/2)^2 × h =π32^2(h+2/3)
(4/3)πr^3 = π32^2(h+2/3)-π32^2 × h
(4/3)πr^3 = π32^2(h+2/3-h)
r = 8 cm

11a.
體積=π4^2 × 9 + (4/3)π4^3 ÷2
=144π+128/3π
=560π/3 cm^311b.總表面面積=π4^2+2π4 × 9 +4π4^2 ÷2
=120π cm^2


2011-04-19 19:38:10 補充：
12a.
體積=π4^2 × 9 + (4/3)π4^3 ÷2
=144π+128/3π
=560π/3 cm^3

12b.總表面面積=π4^2+2π4 × 9 +4π4^2 ÷2
=120π cm^2