Question

30分之1+42分之1+56分之1+72分之1+90分之1+110分之1=?

Answer 1

1/30+1/42+1/56+1/72+1/90+1/110

=1/5-1/6+1/6-1/7+1/7-1/8+...1/9-1/10+1/10-1/11

=1/5-1/11

=6/55