3.7*0.15+2.1*0.45=3.7*0.15+6.3*0.15=(3.7+6.3)*0.15=10*0.15=1.5
3.7*0.15+2.1*0.45 =3.7×0.15+2.1×3×0.15=0.15×（3.7+6.3）=0.15×10=1.5提示：把0.45拆成3×0.15
