(3又1/3+5又2/4+7又3/5+...+57又28/30)/(1又2/3+2又3/4+3又4/5+...28又29/30)-1
=(2又4/3+4又6/4+6又8/5+...+56又58/30)/(1又2/3+2又3/4+3又4/5+...28又29/30)-1
=2-1
=1