The problem of permutation and combination is imminent.

1 There are two situations in this question: ① Four pairs of socks are exactly two pairs, which is equivalent to taking two pairs from five pairs of socks. The method is C (5 5,2) =10. There is only one pair of four socks, and the other two are not a pair. The method is carried out step by step: first, take out a pair of socks from five pairs, C (5 5,65438+. Then take two pairs from the remaining four pairs, each pair 1, and use the method of c (4,2) c (2, 1) C (2, 1) = 6× 2× 2 = 24. According to the principle of step by step counting, we can see that there are some methods at this time. ∴ The overall method is10+120 =130. This problem is better calculated by "total dislocation arrangement". The arrangement number of five balls out of their respective positions is 44, and the arrangement number of four balls out of their respective positions is 9. If there is only one ball in its own position, the arrangement number is 5×9=45. At least two balls are the same as the numbers in the box =5! -44-45=3 1 species.