设a=1/2*3/4*5/6*.99/100
b=2/3*4/5*6/7*.100/101
a*b=1/2*2/3*3/4*4/5*.99/100*100/101=1/101
因为 1/2 < 2/3; 3/4 < 4/5; 5/6 < 6/7.99/100 < 100/101
所以 a