8个正品里面取1个，取2次，即是C(8,1)*C(8,110个产品里面取1个，取2次，即是C(10,1)C(10,1)所以得C(8,1)*C(8,1)/C(10,1)C(10,1)=64/100=0.64
(8/10)^2=16/25
(8/10)*(8/10)=64%
8/10×8/10=16/25
80%x80%=64%
