解:(1)2:4:8,
=(2÷2):(4÷2):(8÷2),
=1:2:4;
(2)18:27:45,
=(18÷6):(27÷9):(45÷9),
=2:3:5;
(3)
,
=(
):(
):(
×6),
=3:2:1;
(4)
,
=(
×8):(
×8):(1×8);
=9:5:8;
(5)0.3:0.15:0.45,
=(0.3×
):(0.15×
):(0.45×
),
=2:1:3;
(6)1.6:2.4:4,
=(1.6×
):(2.4×
):(4×
),
=2:3:5.
故答案为:1:2:4,2:3:5,3:2:1,9:5:8,2:1:3,2:3:5.
分析:根据比的基本性质作答,即比的前项和后项同时乘或除以一个数(0除外)比值不变.
点评:此题主要考查了化简比的方法,另外还要注意化简比的结果是一个比,它的前项和后项都是整数,并且是互质数.