题干

有3个完全相同的小球,把它们分别标号为1,2,3,放在一个不透明的口袋中,从口袋中随机摸出一个小球,记下标号后放回,再从口袋中随机摸出一个小球,记下标号.用画树状图(或列表)的方法,求两次摸出的小球号码恰好都大于1的概率.
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答案(点此获取答案解析)

解:画树状图得:

由图可得共有9种等可能的结果,其中两次摸出的小球号码恰好都大于1的有4种结

同类题1

阅读短文,从每题所给选项中选出可以填入空白处的最佳选项。

    Once there lived a poor family in our town. They were so poor that there was almost(几乎)1 in the house but a pot(罐) 2 a broken table. In it there was a little rice. They 3the rice from their neighbour for the coming New Year. On New Year's Eve(除夕夜), the wife already fell asleep, but the husband was 4 in bed, worrying about their life. Suddenly he heard someone breaking into the room.

    “It must be a thief(小偷),” he thought, “5 it doesn't matter. The thief can steal(偷) nothing.”He didn't shout or move. But he kept6over the thief.

    The thief came into the house and was only7 in the rice under the table.

    “But8can I take it away?” the thief thought hard. Then he had an idea. He9 his coat, put it on the ground between the bed and the table and turned around to take the 10 .

    Now the husband knew11the thief would do. He picked up the coat quickly and covered himself with it12the thief turned back.

    The thief took the pot, and poured(倒) the rice onto the coat. Then he began to feel it. But he was13 to find that his coat was gone.

    “Hey,” he shouted out. The14 woke up the wife. She asked her husband, “Did you hear any sound? Maybe there is a thief in the room.”

    “Shut up! (闭嘴)” replied her husband, “15 to sleep. There is no thief in the room.”

    “That's impossible,”the thief shouted loudly, “If there isn't a thief, then, where is my coat?”

同类题4

极右翼思潮是一种民族——民粹主义、排外主义以及法西斯主义的综合思想体系,其思想核心是种族优越论。20世纪30年代极右翼势力(德国纳粹党、日本军国主义势力)给人类带来了前所未有的灾难——第二次世界大战。今天极右翼思潮在欧洲、日本再次沉渣泛起,引起了国际主流社会的高度警惕。关于20世纪90年代以来西欧极右翼思潮再度兴起的原因,一些学者做了如下的分析:

(一)欧洲自20世纪90年代以来经济发展缓慢甚至倒退使各国财政预算吃紧,高额福利制度难以为继,大量失业人群无所事事,又导致了种族冲突和暴力犯罪活动猖獗,社会治安环境恶化等。人们的安全感大幅下降,极右翼势力紧紧抓住这些问题大做文章,以蛊惑人心获得民众支持。

(二)移民问题所引起的利益、文化冲突。由于一体化、全球化、战乱因素导致的大范围大规模的移民、非法移民,对欧洲的就业和社会福利等形成冲击,同时由于移民本身存在诸多负面影响、移民文化与主流文化的融合难等,尤其引起了中下层人士的强烈不满。这些处在社会底层的人尤其是失业者的排外情绪与极右翼势力的反移民主张不谋而合。

(三)欧洲各国主流政党在解决当前经济社会问题时表现不力,竞选时的承诺大多是一纸空文,从而让普通民众失望。一些国家主流政党经常陷入种种腐败丑闻,对民众的影响力下降。而与之相比,极右翼政党大搞平民化、底层化形象,改变竞选策略、淡化激进措施,更多借助于一些具体的经济社会问题吸引右翼极端分子、小商人、部分原左翼政党选民、青年失业人员甚至一定数量的上层选民的关注和选票,其中特别是工人阶级的支持率上升。

人们在惴惴不安中看到, 2017年法国大选在即,极右翼政客勒庞在民调中处于领先地位;日本试图修改和平宪法,不断扩充军队,在学校对儿童推行“战前教育”,教儿童唱军歌,让儿童背诵明治天皇教育敕语……