记An=1/(n+1)+1/(n+2)+...+1/(2n),n>=2.A(n+1)=1/(n+2)+1/(n+3)+...+1/(2n)+1/(2n+1)+1/(2(n+1)),A(n+1)-An=1/(2n+1)+1/(2(n+1))-1/(n+1)=1/(2n+1)-1/(2(n+1))>0,即An是严格增的序列.依题意,m/72