0.11*9*0.19+0.99*0.81
=0.99*0.19+0.99*0.81
=0.99*(0.19+0.81)
=0.99*1
=0.99
0.9/3.05*0.9*3.05
把3.05约分
0.9/3.05*0.9*3.05
=0.9*0.9=0.81