如图
48.5×10.2-4.85×2=48.5×10.2-48.5×0.2=48.5×(10.2-0.2)=48.5×10=485
=48.5×10.2-48.5X0.2=48.5x(10.2-0.2)=48.5X10=485
48.5×4.85=48.5×(10+0.1)=48.5×10+48.5×0.1=485+4.85=489.85