1/1*2=(2-1)/1*2=2/1*2-1/1*2=1-1/2
1/2*3=(3-2)/2*3=3/2*3-2/2*3=1/2-1/3
……
1/99*100=(100-99)/99*100=100/99*100-99/99*100=1/99-1/100
所以原式=1-1/2+1/2-1/3+……+1/99-1/100
=1-1/100
=99/100
1\1*2+1\2*3+1\3*4+......+1\99*100
=1-1/2+1/2-1/3+……+1/99-1/100
=1-1/100
=99/100