分类：教育/科学-理工学科-数学
问题：数学1.1/12+1/20+1/30+1/42+1/56+1/7 
1.1/12+1/20+1/30+1/42+1/56+1/72+1/90
回答：原式=[1/(3*4)]+[1/(4*5)]+[1/(5*6)]+……+[1/(9*10)]

=[(1/3)-(1/4)]+[(1/4)-(1/5)]+[(1/5)-(1/6)]+……+[(1/9)-(1/10)]

=(1/3)-(1/4)+(1/4)-(1/5)+(1/5)-(1/6)+……+(1/9)-(1/10)

=(1/3)-(1/10)

=7/30.