0.75*15+4.5*2.5=?

0.75*15+4.5*2.5
=0.75*15+45*0.25
=（0.75+0.25）*15+0.25*（45-15）
=15+7.5
=22.5

化成分数计算
原式＝（3/4）*15+（9/2）*（5/2）
＝45/4＋45/4
＝45/2＝22.5

0.75*15+4.5*2.5 = 22.5
0.75*15+15*3*0.25=0.75*15+15*0.75=30*0.75=3*7.5=22.5

0.75*15+4.5*2.5=2.5*0.3*15+4.5*2.5=2.5(0.3*15+4.5)=22.5

=(3/4)*3*5+0.5*9*0.5*5
=9*5/4+9*5/4
=9*5/2
=22.5