So the probability of failure is 1-2/5=3/5.
The first method is divided into two possibilities.
1. Where a (2,2) stands for picking two pieces, the quality inspector just picked two pieces of defective products and arranged them.
2.C (2, 1) C (4, 1) A (2,2) means that only one defective product is drawn and the other is good, so C(2, 1)C(4,1) draws two pieces in sequence.
The second type
C(2，2)+C(2， 1)C(4， 1)]/C(6，2)= 1
1. Where c (2,2) stands for two pieces, the quality inspector just picked up two pieces of defective products.
2.C(2, 1)C(4, 1) means that only one defective product is drawn and the other is good, so C(2, 1)C(4, 1).
Pay attention to the order, the order, or not at all.