Mathematical permutation and combination of senior three

1, a subset of m * * * 2 10 = 1024 (this is a formula to remember).

2. The ternary subset of m is c (10/0,3) = (10 * 9 * 8)/(3 * 2 *1) =120.

3.A ( 10，3) = 10 * 9 * 8 = 720。

4. Choose three elements from 10, and only one combination is a>b>C, so there is C (10/0,3) =120.

5.a and C are interchangeable, so there is 2 * c 2*C( 10/0,3) = 240.

1, from left to right, from high to low, so there is only 1 arrangement.

2. After the middle of the highest station, the symmetrical two can be interchanged, so there is an arrangement of 2*2*2*2= 16.

There is no female student selection method with c (5,4) = 5, but all different choices have c (8,4) = 70.

So at least one girl has 70-5=65 choices.