题干

有一个圆柱,底面直径是4厘米,高是9厘米.从下底面起沿着高的
2
3
处,与底面平行地把圆柱切成上、下两部分.
①上部分的侧面积是下部分侧面积的百分之几?
②上部分的体积是下部分体积的百分之几?
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答案(点此获取答案解析)

解:① 4×3.14×9×(1-23)÷(

同类题3

阅读理解

B

    Shu-How Lin was born on August 23,1988 in California in the USA.He's the newest well-known NBA professional basketball player. His ancestors lived in Fujian Province in China.In 1977,his parents moved to America.Although they live in the USA, they know they are Chinese. And they love their motherland. They try their best to earn more honor(争光)for China.

    When Shu-How was at high school, he showed a great interest in playing basketball. He practiced basketball much harder than any other student in his school. Because of him, the school team became the champion of all the high schools in America, which had never got a champion before. Meanwhile(同时),he studied particularly hard during high school. He always got "A" in most of his subjects.

    After high school, his dream was to join a university, which was famous for basketball, to major in basketball. But none of these universities in America accepted him. They thought that he was just a Chinese and a Chinese could hardly become an excellent professional basketball player. He felt so sad and he had to attend Harvard University by his good grades, where professional basketball players are not wanted. But before long, he became the first man in Harvard who entered NBA after 1954.

    Shu-How never gave up his basketball dream. He joined several NBA teams, but he was never given a chance to show himself in each game. One day, two players of his team were badly hurt. There were no more players who could play the game. The coach had to let Shu-How go for it. This was a great chance for him. He showed his talent in this game. He got 25 scores!

    After that, Shu-How became one of the most outstanding basketball players around the world. He set a great example to all of us. According to him, we know nothing is impossible if we try our best.

同类题5

阅读下面的说明文,完成下列小题。

奇特的年轮

       ①人们所熟知的年轮,是树木的年轮。一棵树被锯倒了,数一数树墩上有多少圈条纹,人们就知道这棵树有多大年龄了。另外,树木的年轮里,还储存着当地的气候、地震、火山爆发和水灾旱灾等丰富的自然信息。因此,科学家十分重视从树木的年轮里获取蕴藏着的科学信息资料。

       ②植物中不仅树木有年轮,水仙花也有年轮,它的年轮在它的“蒜头”上,有一个年轮的,开花期短;有三个年轮的,开花期长。因此,有经验的育花者,往往选取年轮多的水仙头,以便使花期长些。

       ③不仅植物有年轮,动物亦有年轮。鲤鱼等鱼类的年轮是其鳞片上的宽窄分界的条纹。令人不解的是,并非所有的鱼的年轮都在鳞片上,大马哈鱼的年轮在它们的背鳍上,大、小黄鱼的年轮却在它们的耳石上。

       ④牛、羊的年轮在它们的犄角上,所以又称为“角轮”。龟、鳖的年轮在它们的背甲上。蚌、贝和螺的年轮在它们的壳上。

       ⑤腔肠动物珊瑚虫的年轮是它们表壁上有粗细之分的规则形条纹。珊瑚虫不仅有它们的年轮,而且还有它们的“日轮”。一年为365日,那么它们便在自己的体壁上划下365条环纹。

       ⑥兔子和黄鼠狼这样的动物也有年轮,年轮在它们的骨头上,不过,要借助显微镜才能观察到。

       ⑦有些鸟也有年轮:据说,美国科罗拉多州的一位山地生物实验室工作人员捉住一只熊蜂鸟,发现近爪处腿皮上有环圈,根据环圈判断,这只鸟已有11岁了,从而否定了一般认为熊蜂鸟的寿命只有8年的说法。

       ⑧日本科学家最先发现人也有年轮,是在人的头颅里面,通过声波可以检测出一个人的实际年龄。如果检测器的声波频率与被检测人的实际年龄相符,人体便会做出反应,从而在荧屏上显示出来。目前,这一先进的科学技术已应用于实际生活中,如用它来检测大型运动会参赛人员的实际年龄,或是应用到刑事案件的侦破中,用以检测涉嫌人员或罪犯的实际年龄,从而为破案提供重要的线索和有力的证据。

       ⑨按理说,一切生物都应该有它们各自的年龄,只不过是有的已经被发现,更多的没有被发现罢了。科学家们正努力探索生物年轮的奥秘,以便有更多的发现,进而造福于人类。