其实常人能看出来的也算是简便方法了,比如98×2=196都能看的出,所以
98×0.2+0.4
=19.6+0.4
=20
其实这道题有另外方法让大家看起来更加简便,那就是把0.2提出去,即
98×0.2+0.4
=98×0.2+2×0.2
=0.2×(98+2)
=0.2×100
=20
98*0.2+0.4=98*0.2+2*0.2=0.2*(98+2)=20
(100+2)×0.2+0.4
=20-0.4+0.4
=20
简便就是0.4=2×0.2
98×0.2+2×0.2=(98+2)×0.2=20