Current location - Training Enrollment Network - Mathematics courses - In 2006, Hunan college entrance examination rolled up 6 questions about science mathematics. What is the detailed solution?
In 2006, Hunan college entrance examination rolled up 6 questions about science mathematics. What is the detailed solution?
The first case is uncontroversial: three projects are located in three cities: P43 = 24.
In the second case, you should have a better understanding: C32 (choose two of the three projects to invest in one city) * C4 1 (choose four cities 1)* c 3 1 (choose the remaining three projects 1 invest in the remaining three cities1) = 3 *.