1/2+1/3+2/3+1/4+2/4+3/4+……+58/60+59/60=1/2+(1-2/3+2/3)+(1-3/4+2/4+3/4)+……
=1/2+1+(1+1/2)+(1+1)+(1+1+1/2)+……=2X(1+2+3+……+29)+30X1/2=885
1/2+1/3+2/3+1/4+2/4+3/4+……+58/60+59/60=1/2+(1-2/3+2/3)+(1-3/4+2/4+3/4)+……
=1/2+1+(1+1/2)+(1+1)+(1+1+1/2)+……=2X(1+2+3+……+29)+30X1/2=885