3.5×40.2=3.5×(40+0.2)=3.5×40+3.5×0.2=140+0.7=140.7
3.5x40.2 =3.5x40+3.5x0.2 =140+0.7 =140.7对
3.5x40.2=3.5x40+3.5x0.2=140+0.7=140.7
