2.9*0.45+0.29*4.2+0.
问题描述：
2.9*0.45+0.29*4.2+0.
答
2.9*(0.45+0.42+0.13)=2.9*1=2.9
答
=2.9*0.45+2.9*0.42+2.9*0.13
=2.9*(0.45+0.42+0.13)
=2.9*1
=2.9