题目内容：

42之1+56分之1+72分之1+90分之1+110分之1请做吧^.^
过程答案写清楚!

优质解答

1/42+1/56+1/72+1/90+1/110
=1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)+1/(10*11)
=1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11
=1/6-1/11
=5/66