Current location - Training Enrollment Network - Mathematics courses - The most difficult math problem in senior two.
The most difficult math problem in senior two.
1. Considering driving one person's car first, there are three arrangements, namely A( 1, 3)=3, the remaining four people have three jobs, and the rest can be arranged at will. Considering that every job needs people, a job must have two people, so you can choose two people first. There are six kinds of C (2 2,4) =1

2. If two people drive, there are three kinds of C (2,3) = the other three people do three kinds of jobs, which is one kind of A (3,3), so the overall arrangement scheme is C (2,3) × A (3,3) =18.

72+ 18 = 90 species.