用简便方法计算 5.6X3.9+0.44X39=5.6Ⅹ3.9+4.4X3.9=(5.6+4.4)X3.9=10X3.9=39
5.6×3.9+0.44×39 =5.6×3.9+4.4×3.9 =（5.6+4.4）×3.9 =10×3.9 =39
