|1/2011-1/2010|+|1/2010-1/2009|+|1/2009-1/2008|+...+|1/2-1| =(1/2010-1/2011)+(1/2009-1/2010)+……+(1-1/2) =-1/2011+1/2010-1/2010+1/2009+...-1/2+1 =-1/2011+1 =2010/2011