百分之十二点五
=12.5/100
=25/200..分子分母同乘2
=1/8..分子分母同除25
百分之三十七点五
=37.5/100
=75/200.分子分母同乘2
=3/8.分子分母同除25
百分之五十
=50/100
=1/2
=4/8
所以
百分之十二点五：百分之三十七点五：百分之五十
=1/8:3/8:4/8
=1:3:4