1-1/2+1/3-1/4+1/5-1/6+1/7-1/8+1/9-1/10 =(1-1/2-1/4-1/8)+(1/3-1/6+1/9)+(1/5-1/10)+1/7=1/8+5/18+1/5+1/7=13/40+53/126=1879/2520