三棱台ABC-A1B1C1中,AB∶A1B1=1∶2,则三棱锥A1-ABC,B-A1B1C,C-A1B1C1的体积之比为( C )
A.1∶1∶1 B.1∶1∶2
C.1∶2∶4 D.1∶4∶4
[解析] 设棱台的高为h,S△ABC=S,则S△A1B1C1=4S.
VC-A1B1C1=S△A1B1C1·h=Sh,
又V台=h(S+4S+2S)=Sh,
∴VB-A1B1C=V台-VA1-ABC-VC-A1B1C1
=Sh--=Sh.
∴体积比为1∶2∶4.∴应选C.
A.1∶1∶1 B.1∶1∶2
C.1∶2∶4 D.1∶4∶4
[解析] 设棱台的高为h,S△ABC=S,则S△A1B1C1=4S.
∴VA1-ABC=S△ABC·h=Sh,
VC-A1B1C1=S△A1B1C1·h=Sh,
又V台=h(S+4S+2S)=Sh,
∴VB-A1B1C=V台-VA1-ABC-VC-A1B1C1
=Sh--=Sh.
∴体积比为1∶2∶4.∴应选C.