(1+1/2+1/3+1/4+1/5+1/6)x(1/2+1/3+1/4+1/5)-(1/2*1/3+1/4+1/5+1/6)x(1/2+1/3+1/4+1/5) 用简便算法

(1+1/2+1/3+1/4+1/5+1/6)x(1/2+1/3+1/4+1/5)-(1/2*1/3+1/4+1/5+1/6)x(1/2+1/3+1/4+1/5)=（1/2+1/3+1/4+1/5）×[(1+1/2+1/3+1/4+1/5+1/6)-(1/2*1/3+1/4+1/5+1/6)]=(1/2+1/3+1/4+1/5)×1=1/2+1/3+1/4+1/5=30/60+20/60+...