问题 解答题

(1甲乙两人都进行射击训练,如果两人击中目标的概率都是0.6,求:

)2人都击中目标的概率;

(2)其中恰有1人击中目标的概率;

(3)至少有1人击中目标的概率.

答案

(1)甲乙两人各进行1次射击,如果2人击中目标的概率都是0.6,

两个人能否击中是相互独立的,

∴2人都击中目标的概率是0.6×0.6=0.36;

(2)恰好有1人击中,表示甲击中乙没有击中,或表示甲没有击中乙击中,这两个事件是互斥事件,

根据相互独立事件和互斥事件的概率公式得到:P=0.4×0.6+0.4×0.6=0.48;

(3)至少有一人击中目标的对立事件是没有人击中目标,

没有人击中目标的概率是(1-0.6)(1-0.6)=0.16,

根据对立事件的概率公式得到:至少一个人击中目标的概率是1-0.16=0.84.

选择题
完形填空

第二节:完形填空(共20小题;每小题1.5分,满分30分)

阅读下面短文,掌握其大意,然后从21~40各题所给的四个选项(A、B、C和D)中,选出最佳选项。

Jane’s mother worked on the farm from dawn till dark, which just could make ends meet. To make Jane live a   21  life. Mother was very carful about spending money.   22 , Jane didn’t understand her. Every day Mother was busy with her  23   while Jane was studying at school, so they had little time to enjoy themselves. 

One day, Mother realized Jane was unhappy and even  24  to her, so she decided to go   25 with Jane to make Jane happy.

On Sunday morning they went happily to the snowfield. Since they were   26  in white clothes, the manager advised them to buy ski clothes. He said   27 there was an accident, they might be easily  28  in their ski clothes. Mother couldn’t   29 them, so she refused.

Then they went skiing in their white clothes. They were skiing happily on the   30   when suddenly the snowfield began to  31 . It was the snowslide(雪崩). They ran a long way and  32   the snowslide finally, but they couldn’t find their way. Later, a helicopter was flying above,  33 people on it couldn’t see or hear them. Jane was  34   because she had hurt her head seriously and  35 dropped on the snow. Just then an idea struck Mother. She pierced (刺破) her wrist  36  and then bright red blood dropped down on the snowfield. A red SOS was on the snow. At last Jane  37 , but Mother died.

Every time I   38  the blood dropping onto the snowfield, I feel   39 . I believe anyone who hears the tragedy will  40  Mother for her selfless love to her daughter.

21. A. happy         B. healthy            C. busy              D. meaningful

22. A. Moreover      B. However          C. Anyway            D. Though

23. A. writing         B. housework         C. work              D. research

24. A. unfriendly       B. loyal              C. kind               D. cruel

25. A. skating              B. dancing           C. hiking             D. skiing

26. A. all             B. both              C. either              D. every

27. A. now that         B. in case            C. as though          D. even if

28. A. searched         B. examined          C. found             D. caught

29. A. pay             B. manage           C. afford              D. stand

30. A. mountain       B. farmland          C. playground         D. snowfield

31. A. change         B. melt              C. shake               D. jump

32. A. escaped          B. passed             C. experienced         D. overcame

33. A. but             B. so                C. since               D. while

34. A. in despair        B. in danger          C. in peace            D. in ruins

35. A. hair            B. blood             C. tears               D. jewels

36. A. carefully        B. slowly            C. immediately         D. hardly

37. A. cried           B. died              C. woke              D. survived

38. A. find out         B. think of                 C. suffer from         D. come across

39. A. satisfied        B. curious            C. anxious            D. painful

40. A. admire          B. envy             C. reward             D. thank