A class of probability problems, find the solution method

The denominator is 7! No problem.

1. A has a 6 on the left! In this case, A has 6 on the right! In this case, probability = 2 72, a on the left and b on the right has 5! In this case, B has 5 on the left and A on the right! case, probability = 1 21

3. A means A is on the edge, B means B is on the edge, p(a+b) = p(a) + p(b)-p(ab) = 4 7-1 21 = 11 21

Use permutations: A or B has 2 6 on the side! +2×6！-2×5！kind of situation.

1a is on the side, then the position of a (left or right) is determined, and the other 6 people can be lined up as they please, a22xa66.

It's all on the side, maybe A on the left, B on the right, maybe the other way around, so A22, the other 5 don't care, A55

Answer: A22xA55

3a is on the side, a66xa22 b, and the same is true for the case where they are on the side twice, minus a55xa22

A is on the left, B is on the right, and there are 5! In this case, B has 5 on the left and A on the right! case, probability = 1 21

Since the full probability event is 1, it is 1 3 to go to b and 1 6 to c.

So, p c(6,3)(1 2) c(3,2)(1 3) c(1,1)(1 6).

Can't see clearly,,, you're lazy enough.

Because the amount of each policyholder's claim is changed to be buried xi independently and distributed with the annihilation search.

Therefore, its sum x= xi approximately obeys a normal distribution.

That is, the total amount of compensation x n(,(8*10 4) 2)p(x>=

Share a solution.

1), according to the nature of the distribution law of discrete random variables, there is p(x=k)=1. ∴4c+3c+2c+3c=1。∴c=1/12。

2), x=1 has no corresponding p(x=k) value, p(x=1)=0.

3), the distribution function of x is, f(x)=0,x<-4;f(x)=f(-4)=4c=1/3，-4≤x<；f(x)=f(-4)+f(-2,5)=4c+3c=7/12，-2,5≤x<-2；f(x)=f(-4)+f(，-2≤x<；f(x)=f(-4)+f(，x≥。

FYI.