问题 解答题
某网站就观众对2010年春晚小品类节目的喜爱程度进行网上调查,其中持各种态度的人数如下表:
喜爱程度喜欢一般不喜欢
人数560240200
(1)现用分层抽样的方法从所有参与网上调查的观众中抽取了一个容量为n的样本,已知从不喜欢小品的观众中抽取的人数为5人,则n的值为多少?
(2)在(1)的条件下,若抽取到的5名不喜欢小品的观众中有2名为女性,现将抽取到的5名不喜欢小品的观众看成一个总体,从中任选两名观众,求至少有一名为女性观众的概率.
答案

(1)采有分层抽样的方法,样本容量与总体容量的比为:n:1000(2分)

则不喜爱小品观众应抽取

n
1000
×200=5人

∴n=25.(5分)

(2)由题意得,女性观众抽取2人,男性观众抽取3人,

设女性观众为a1,a2,男性观众为b1,b2,b3

则从5位不喜爱小品的观众中抽取两名观众有10种可能:

(a1,a2),(a1,b1),(a1,b2),(a1,b3),(a2,b1),(a2,b2),(a2,b3),

(b1,b2),(b1,b3),(b2,b3),(8分)

其中抽取两名观众中至少有一名为女性观众有7种可能:

(a1,a2),(a1,b1),(a1,b2),(a1,b3),(a2,b1),(a2,b2),(a2,b3),(10分)

∴从5位不喜爱小品的观众中抽取两名观众,至少有一名为女性观众的概率为

7
10
(12分)

阅读理解

阅读理解.

     There once was a group of tiny frogs(青蛙) who held a running competition. The goal

was to reach the top of a very high tower. A big crowd had gathered around the tower to

see the race and cheer on the contestants.(选手)

     The race began…

     Honestly, no one in the crowd really believed that the tiny frogs would reach the top of

the tower. You heard statements such as:

     "Oh, it's too difficult!"

     "They will NEVER make it to the top."

     "Not a chance that they will succeed. The tower is too high!"

     The tiny frogs began falling down, one by one…

     …except for those who in a fresh tempo(节奏) were climbing higher and higher…

     The crowd continued to shout, "It is too difficult! No one will make it!"

     More tiny frogs got tired and gave up… But one continued higher and higher and

higher …This one wouldn't give up!

    In the end, everyone else had given up climbing the tower, except for the one tiny frog

which, after a big effort(努力), was the only one who reached the top!

     Then all of the other tiny frogs naturally wanted to know how this tiny frog managed to

do it.

     A contestant asked the frog how he had found the strength to reach the goal. It turned

out that the winner was deaf.

1. The big crowd's statements showed that ________.

A. they tried to discourage the contestants

B. they thought the contestants would give up

C. they didn't believe that the contestants would succeed

D. they hoped that they could watch a wonderful game

2. As the crowd expected, the tiny frogs began to ________.

A. climb higher and higher

B. fall down one by one

C. make it to the top

D. beat each other

3. When asked how the succeeded, the winner ________.

A. didn't mention the secret

B. couldn't hear or answer at all

C. was too shy to answer

D. didn't care about it at all

4. The story mainly tells us that ________.

A. nothing is impossible if we put our heart into it

B. a deaf frog can run much faster than others

C. we shouldn't care about what others say if we want to succeed

D. we needn't spend too much time in looking for special skills.

单项选择题