题干

下列问题中是古典概型的是(  )

A:种下一粒杨树种子,求其能长成大树的概率

B:掷一颗质地不均匀的骰子,求出现1点的概率

C:在区间1,4上任取一数,求这个数大于1.5的概率

D:同时掷两枚质地均匀的骰子,求向上的点数之和是5的概率

上一题 下一题 0.0难度 选择题 更新时间:2017-05-28 01:33:58

答案(点此获取答案解析)

D

同类题2

【加试题】德国数学家哥德巴赫曾猜测:任何大于6的偶数都可以分解成两个素数(素数对)的和。但有些偶数可以分解成多种素数对的和,如: 10=3+7,10=5+5,即10可以分解成两种不同的素数对。

小敏编写了一个VB程序,用来求一个偶数(6到100之间)可能存在多少这样的素数对(注: A+B与B+A认为是相同素数对,不重复统计),并把这些结果输出到一个列表框中,通过逻辑推理,小敏发现这些素数对都是奇数,所以她只需要验证奇数的素数对即可。运行界面如图所示,程序代码如下。但加框处代码有错,请改正。

 

Dim IsPrime(100) As Boolean  '用来存储是否素数,True为素数,False为非素数

Private Sub Command1_Click()

    Dim x As Integer, y As Integer, i As Integer, num As Integer

Call Init  '调用Init函数

    x = Val(Text1.Text)

y = x \ 2

num = 0

For i = 3 To y Step 2

                 '①

num = num + 1

            List1.AddItem Str(x) + "=" + Str(i) + "+" + Str(x - i)

        End If

    Next i

    Label2.Caption = "偶数" + Str(x) + "共有" + Str(num) + "个素数对。"

End Sub

Sub Init() '初始化IsPrime数组的值

    Dim i As Integer, j As Integer, x As Integer

    For i = 3 To 100 Step 2

        x = Int(Sqr(i))

                            '②

            If i Mod j = 0 Then Exit For

        Next j

        If j > x Then IsPrime(i) = True Else IsPrime(i) = False

    Next i

End Sub

①____ ②____ 

同类题3

阅读下列短文,根据短文中的信息完成文后表格。在横线上写出空缺处所填单词的正确形式。(每空一词)

    Recently, the relationship between the two countries got worse because of the Diaoyu Islands.

    The Japanese government signed a contract(合同) on Sep 11 with the Kurihara family. It was to pay the so-called “private(私人的) owner” 2.05 billion yen (166 million yuan) to “buy” part of China's Diaoyu Islands.

    Anti-Japan(反日) feeling grew strongly among Chinese people. Many people walked into the streets and shouted out “Diaoyu Islands are China's.” Some have decided not to buy Japanese products any more. “I am boycotting(抵制) Japanese goods as a show of support. I'll work hard to make the country much stronger,” Liu Xiushan, 33, a lawyer in Beijing said to China Daily.

    However, some didn't show their anger in the right way. They broke cars and stores of Japanese brands. Some used rude words. These actions are bad for our position and image. Some actions were against law.

    Li Jingjun, a 17-year-old high school student in Guangzhou, was shocked by what he learned from TV and the Internet. He joined protects(抗议) in his city on September 15. But he acted differently. He called for rational (理智的) actions.

    “We have every right to say the Diaoyu Islands belong to us, but we should watch our behaviour. Bad manners can harm our dignity(尊严) and sense of justice(正义感)” ,said Li Jingjun.

The event


The Japanese____signed a contract to “buy” part of China's Diaoyu Islands.

The____


The relationship between the two countries____worse.

Anti-Japan feeling grew strongly____Chinese people, many people walked into streets,____“Diaoyu Islands are China's.”

Some people have____to buy Japanese products.

Some people did something against the law like____cars and stores of Japanese brands.

The conclusion


____we have every right to say the Diaoyu Islands belong to us, we should under the law and watch____we do. What's more, we should make our country____.