1/(1*2)+1/(2*3)+...+1/(49*50)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+...+(1/49-1/50)
=1-1/2+1/2-1/3+1/3-1/4+...+1/49-1/50
=1-1/50
=0.98