Solution: After putting three cars, there are still seven seats, which are 5, 1, 1. At this time, 4×3= 12 kinds of vacancies were placed next to the three cars. If it is divided into 5 and 2, * * * has = 12 species, 24 species; Random parking * * * Probability is 24/ 120=20%.
Combination:
In combinatorial mathematics, the Combination of elements of a set is a subset. K- combination of s is a subset of s with k elements. If the elements of two subsets are exactly the same and the order is different, they are still regarded as the same combination, which is the difference between combination and arrangement.