数学题简算

使用扩缩法
3.14*78+0.314*78+314*0.22+31.4*0.22
=3.14*78+3.14*7.8+3.14*22+3.14*2.2
=3.14*(78+7.8+22+2.2)
=3.14*100+3.14*10
=314+31.4
=345.4

269.412+75.988=345.4

3.14*(78+7.8+22+2.2)=3.14*(100+10)=3.14*110=345.4

变形一下 =31.4*78+31.4*100*0.22+0.314*78+0.314*22
=31.4*（78+22）+0.314*（78+22）
=3140+31.4
=3171.4

3.14*78+0.314*78+314*0.22+31.4*0.22
=3.14*78+3.14*7.8+3.14*22+3.14*2.2
=3.14*(78+7.8+22+2.2)
=3.14*100+3.14*10
=314+31.4
=345.4

0.314*780+0.314*78+0.314*220+0.314*22
=0.314*（780+78+220+22）
=0.314*1100
=345.4