某校为了解高二学生A,B两个学科学习成绩的合格情况是否有关,随机抽取了该年级一次

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问题:

某校为了解高二学生A,B两个学科学习成绩的合格情况是否有关,随机抽取了该年级一次期末考试A,B两个学科的合格人数与不合格人数,得到以下2X2列联表:
A学科合格人数A学科不合格人数合计
B学科合格人数402060
B学科不合格人数203050
合计6050110
(1)据此表格资料,你认为有多大把握认为“A学科合格”与“B学科合格”有关;
(2)从“A学科合格”的学生中任意抽取2人,记被抽取的2名学生中“B学科合格”的人数为X,求X的数学期望.
附公式与表:K2=
n(ad-bc)2
(a+b)(c+d)(a+c)(b+d)

P(K2≥k)0.150.100.050.0250.0100.005
K2.0722.7063.8415.0246.6357.879
考点:独立性检验的基本思想及其初步应离散型随机变量的期望与方差
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阅读短文还原句子,其中有一多余选项
It’s the best medicine.
Many old people like watching TV.
You must stay safe when you are playing sports.
You must avoid(避免) smoking and drinking.
So don’t go to school without breakfast.
You need to have healthy eating habits. Breakfast gives you enough energy(能量) for the morning.  _______1_______ Fruit and vegetables are good for your health, but fast food, like potato chips, will make you fat and unhealthy. So eat the right food to keep you healthy.
Playing sports can also help you keep fit. But sometimes it may cause accidents(引发事故). _______2_______
Happiness is important for your health. _______3_____ When you are ill, try to be happy and you’ll feel better. On the other hand, you may feel sick if you are always unhappy. So, be happy to be healthy.
______4______. Many students thinks it’s cool to smoke and drink. But they don’t know smoking and drinking can cause many illness. You should say no to smoking and drinking.
题型:解答题

如图所示,水平转台高1.25 m,半径为0.2 m,可绕通过圆心处的竖直转轴转动.转台的同一半径上放有质量均为0.4 kg的小物块AB(可看成质点),A与转轴间距离为0.1 m,B位于转台边缘处,AB间用长0.1 m的细线相连,AB与水平转台间最大静摩擦力均为0.54 N,g取10 m/s2

(1)当转台的角速度达到多大时细线上出现张力?

(2)当转台的角速度达到多大时A物块开始滑动?

(3)若A物块恰好将要滑动时细线断开,此后转台保持匀速转动,求B物块落地瞬间AB两物块间的水平距离.(不计空气阻力,计算时取π=3)

题型:解答题

冰雹是冰雹云的产物,多数是超级单体风暴、多单体风暴、()三类强风暴云中的任一种。但较强的雹灾多半是由()风暴云造成。

题型:解答题

当一个程序使用DOS系统功能调用退出用户程序时,在编写INT 21H指令前,应选的指令是______。

A) MOV AL, 01H
B) MOV AL,4CH
C) RET
D) MOV AH,4CH

题型:解答题

在单元组合式集中监视与报警系统中,开关量报警控制单元的逻辑判断环节可用来完成()。

A.逻辑运算

B.逻辑延时

C.状态运算

D.输出控制

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