1/50+2/50+…+49/50
=1/50(1+2+...+49)
=1/50*49*50/2=24.5
1-99/100+98/100-97/100+……+2/100-1/100
=(1-99/100)+(98/100-97/100)+……+(2/100-1/100)
=1/100+1/100+...+1/100
=1/100*50=1/2
1/50+2/50+…+49/50
=1/50(1+2+...+49)
=1/50*49*50/2=24.5
1-99/100+98/100-97/100+……+2/100-1/100
=(1-99/100)+(98/100-97/100)+……+(2/100-1/100)
=1/100+1/100+...+1/100
=1/100*50=1/2