2/1*2*3+2/2*3*4+2/3*4*5+2/4*5*6+.....2/98*99*100=(1/(1*2)-1/(2*3))+(1/(2*3)-1/(3*4))......+(1/(98*99)-1/(99*100))=1/2-1/(99*100)=(50*99-1)/(99*100)=4949/9900