When 30 numbers are divided into 10 and divided into ten groups, they will be arranged and combined according to numbers. The specific formula is C30 10C20 10 for permutation and combination. But the final result is very huge, and no specific calculation is usually made.

Permutation and combination is the most basic concept of combinatorics. The so-called arrangement refers to taking out a specified number of elements from a given number of elements for sorting. Combination refers to taking out only a specified number of elements from a given number of elements, regardless of sorting.

In mathematical problems, especially probability problems, it is often necessary to analyze them by permutation and combination.