In fact, it is 10 ball, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, and draw two from it. . .

* * * There are 10C2=45 possibilities.

The probability of touching 1 for the first time is 1/5, then the probability of touching 5 for the second time is 2/9, and the probability of multiplying 1, 5 is 2/45.

Similarly, the probability of touching 2, 44, 25, 1 in sequence is 2/45.

Now let's discuss the possibility of touching 3, 3.

The probabilities of touching 3 for the first time and the second time are 1/5, 1/9 respectively, and the product is 1/45. . .

Add the above five numbers to get 9/45= 1/5.

The probability that the sum is 6 is 20%