56/47*55=（1+9/47）×55=55+495/47=65又25/47
=56/47*(56-1)=56/47*56-56/47*1=47-56/47=46又56/9
56/47*55（简便计算）56/47*55=56/47*（47+8）=56/47*47+56/47*8=56+448/47=65又25/47
