4.半徑=12/2 = 6

總表面積=4π (6)²x 1/2 + π(6)²

                = 108π

5 半徑= 30.5/2 = 15.25

 所求面積=4π(15.25)²

                 =2920(m²)(準確至3位有效數字)

7 半徑=14/2 = 7

所求體積=1/3 x π (7)² x(20-7) + 4/3 x π (7)³ x 1/2

                =1390 (cm³)(準確至3位有效數字)

8 設半徑=r

 4 π r²=4000

   π r²=1000

       r  = 17.8 (準確至3位有效數字)

13.

∵ 兩個立體體積相等

∴ 1/3 x π (6)² (vo) = 4/3 x π (6)³

                  12 π  (vo)=288 π

                             vo = 24