1/2+1/6+1/12+1/9+1/30
=1/2+1/6+1/12+(1/20+11/180)+1/30
=(1/2+1/6+1/12+1/20+11/30)+11/180
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+11/180
=1-1/6+11/180
=5/6+11/180
=161/180