题目

不用写出过程,只要写一下每一题的答案和大概怎么做的就行了,感激不尽
10.A box contains 6 white marbles,7 red marbles,and 8 blue marbles.
(a) If you choose 3 marbles at random from the box,what is the probability that they are
all the same color?
(b) Suppose instead you choose the 3 marbles one at a time,and each time you choose
a marble,you return it to the box before drawing the next marble.What is the
probability that all three marbles are the same color?
11.If you are dealt 5 cards from a standard 52-card deck,what is the probability that you will
get at least one card of each suit?
12.Suppose 10 couples attend an event,and all 20 people enter a raffle.Four of the 20 people
are selected at random to win $10 in the raffle.What is the probability that at least one
couple takes home $20,which will occur if both the husband and wife win the raffle?
13.Suppose that 10 people attend a gathering.
(a) Suppose the 10 people consist of 5 couples (each consisting of a husband

提问时间：2020-12-18

答案

10（a）(c(3,6)+c(3,7)+c(3,8))/c(3/21);
(b) (6/21)*(6/21)*(6/21)+(7/21)*(7/21)*(7/21)+(8/21)*(8/21)*(8/21);
11.c(1,13)*c(1,13)*c(1,13)*c(1,13)*c(1,48)/c(5,52);
12.c(1,10)*c(2,2)*c(2,18)/c(4,20);
13.(a)A(5,5)*A(5,5)*A(2,2)/A(10,10);
(b)A(5,5)*A(2,2)/A(10,10);