设圆柱的底面积为S,高为h,
则圆柱的体积=Sh,圆锥的体积=
1
3 ×
3
4 S×
5
2 h=
8 Sh,
体积比:Sh÷
8 Sh=
8
5 ;
答:它们的体积比是8:5.
故答案为:8:5.