7.2/4.7*0.5的简便算法：=7.2*0.5/4.7=3.6/4.7
7.2÷4.7×0.05=72/47 ×5/100=36/470=18/235=0.076596
7.2÷4.7×0.05=0.076595744680851063829787234042553
是一个无限循环小数0.076595745
