①0.25×(10+0.4)=0.25×10+0.25×0.4=2.5+0.1=2.6
②8.5×9.9=8.5×(10-0.1)=8.5×10-8.5×0.1=85-0.85=84.15
③13.5×4.28-13.5×3.28=13.5×(4.28-3.28)=13.5×1=13.5
④1.01×101-1.01=1.01×(101-1)=1.01×100=101
①0.25×(10+0.4)=0.25×10+0.25×0.4=2.5+0.1=2.6
②8.5×9.9=8.5×(10-0.1)=8.5×10-8.5×0.1=85-0.85=84.15
③13.5×4.28-13.5×3.28=13.5×(4.28-3.28)=13.5×1=13.5
④1.01×101-1.01=1.01×(101-1)=1.01×100=101