Question

求以概率问题的答案

Suppose that an urn contains 9 balls with the following number labeling and
colors.
Number on ball 1 2 3 4 5 6 7 8 9
Color R W R B W R R W B
R is for red. W is for white. B is for black.

Suppose that we draw two balls from the urn above in succession and without
replacement:

b) What is the probability that the first ball drawn is white, given that we know
it is even?
c) What is the probability that the first ball drawn is even, given that we know it
is white?
d) What is the probability that the second ball drawn is white, given that the
first ball drawn is odd?

Answer 1

假设金塔包含9球，下面的是一些标记和
颜色。
球的号码 1 2 3 4 5 6 7 8 9
色彩 R W R B W R R W B
R是红色。 W为白色。 B是黑色。

假设，我们从以上的金塔不放回的得出两个球：

b ）取出的第一个球是白色的概率是多少，前提是我们知道
它的号码是偶数？
c）取出的第一个球是偶数的概率是多少，前提是我们知道这
是白色的球？
d）第二球是白色的概率是多少,前提是知道第一球是奇数的？

解答:
b)1/2
c)2/3
d)3/8*4/5+2/8*1/5=7/20

Answer 2

鸟语