问题 解答题

某旅游地有甲乙两个相邻景点,甲景点内有2个美国旅游团和2个日本旅游团,乙景点内有2个美国旅游团和3个日本旅游团.现甲乙两景点各有一个外国旅游团交换景点观光.

(Ⅰ)求甲景点恰有2个美国旅游团的概率;

(Ⅱ)求甲景点内美国旅游团数的期望.

答案

(Ⅰ)甲乙两个景点各有一个外国旅游团交换后,甲景点恰有2个美国旅游团有下面几

种情况:①都交换的是美国旅游团,则此时甲景点恰有2个美国旅游团事件A1的概率P(A1)=

C12
C12
C14
C15
=
1
5
.…(2分)  ②都交换的是日本旅游团,则此时甲景点恰有2个美国

旅游团事件A2的概率 P(A2)=

C12
C13
C14
C15
=
3
10
.…(4分)

故P(A)=P(A1)+P(A2)=

1
5
+
3
10
=
1
2
.…(6分)

(Ⅱ)设甲景点内美国旅游团数为ξ,则ξ的分布列为:…(7分)

 ξ 1 2 3
 P 
3
10
 
1
2
 
1
5
Eξ=
3
10
×1+
1
2
×2+
1
5
×3=
19
10
.…(12分)

阅读理解

Normal bicycle safety guides usually tell you to wear you helmet(头盔) and to obey the law in order to avoid being hit on a bike. Is this advice really helpful?

Consider this for a moment: Wearing a helmet will absolutely do nothing to prevent you from getting hit by a car. Surely, a helmet might help you if you get hit, but you No.1 goal should be to avoid getting hit. Plenty of cyclists were killed by cars__________. However, if they had ridden without helmets, yet followed the guidelines listed below, they might still be alive today. So they saying that wearing a helmet is the first and last word in bike safety is, to some degree(在一定程度上), wrong.

The most common bike safety advice is “follow the law”. Ridiculously, most people are already aware that it’s stupid to race through a red light at a crossroads. As a result, it’s clear that the “follow the law” advice isn’t that helpful, either. In addition, following the law is not enough to keep you safe. Here’s an example: The law tells you to ride on the right, but if you ride too far to the right, someone started a parked car could open their door right in front of you and motorists pulling out of driveways and parking lots will be less visible. In that case you were following the law, but could still have been hit.

Then what should we remember in order to keep safe when riding a bike? I will tell you about it in the following paragraph.

小题1:What does the author say about wearing a helmet in the second paragraph?(within 8 words)

_________________________________________________________________________________________

小题2:Which sentence in the passage is the closest in meaning to the following one?

However, nearly everyone knows that riding through hared traffic light is dangerous.

_________________________________________________________________________________________

小题3:Please fill in the blank in the second paragraph with proper words or phrases to complete the sentence.(within 5 words)

_________________________________________________________________________________________

小题4: List the two regular bike safety guides.(within 8words)

_______________________________________②_______________________________________

小题5:Translate the underlined sentence in the third paragraph into Chinese.

__________________________________________________________________________________

选择题