小学五年级简便运算两道!!!!!大家帮忙啊

1、0.64*7.2+3.6*2.72
=0.64*2*3.6+3.6*2.72
=3.6*(1.28+2.72)
=3.6*4
=14.4

2、0.78*0.45*0.1/7.8/0.045
=7.8*0.045*0.1/(7.8*0.045)
=0.1

1.＝4.608＋9.792＝14.4

2.＝0.351*0.1/7.8/0.045
＝0.0351/7.8/0.045
＝0.0045/0.045
＝0.1

3.6*(0.64*2+2.72)=3.6*4=13.6
(7.8*0.1)*(0.045*10)*0.1/(7.8*0.045)=0.1*10*0.1=0.1

3.6*(1.28+2.72)=3.6*4=12.4
下面这一个 一约分就好了 不用算0.1