6个相乘的分数，除了1之外，分子共4个5，分母6个4，再与3个4相乘的话，即约去之前分母的3个4，所以原式=5X5X5X5/（4X4X4）=625/64
5/4x5/4x1/4x1/4x4/5x4/5x4x4=(5/4x4/5)x(5/4x4/5)x(1/4x4)x(1/4x4)=20/20x20/20x4/4x4/4=1x1x1x1=1
