0.05*3.18*400
=0.05*400*3.18
=20*3.18
=63.6

【1.25+1.25+0.125】*0.8
=1.25*0.8+1.25*0.8+0.125*0.8
=1+1+0.1
=2.1

7.5*100.1
=7.5*（100+0.1）
=7.5*100+7.5*0.1
=750+0.75
=750.75

0.25*83.6-4.36*0.25
不能简便

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