(1又2/3)/(3又1/3)=(5/3)/(10/3)=1/2
(2又3/4)/(5又2/4)=(11/4)/(22/4)=1/2
…………
(98又99/100)/(197又98/100)=(9899/100)/(19798/100)=1/2
(1又2/3+2又3/4+3又4/5+...+97又98/99+98又99/100)/(3又1/3+5又2/4+7又3/5+...+195又97/99+197又98/100)
=(1又2/3+2又3/4+3又4/5+...+97又98/99+98又99/100)/[2(1又2/3+2又3/4+3又4/5+...+97又98/99+98又99/100)]
=1/2