如果只乘到1-五分之一就=3/2x5/4x7/6x9/8x11/10x2/3x4/5=7/6x9/8x11/10=693/480如果只乘到1-九分之一就=3/2x5/4x7/6x9/8x11/10x2/3x4/5x6/7x8/9=11/10
答案是231/160
