![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286016_ST/images0.png)
某校从参加高一年级期末考试的学生中抽出60名学生,将其成绩(均为整数)分成六段,[40,50),[50,60),…[90,100]后画出如下图的频率分布直方图,观察图形,回答下列问题:
(1)求第四小组的频率,并补全这个频率分布直方图;
(2)估计这次考试的合格率(60分及60分以上为合格);
(3)把90分以上(包括90分)视为成绩优秀,那么从成绩是60分以上(包括60分)的学生中选一人,求此人成绩优秀的概率.
考点分析:
相关试题推荐
已知数列{a
n}的前n项和为S
n,满足S
n+2n=2a
n(1)证明:数列{a
n+2}是等比数列.并求数列{a
n}的通项公式a
n;
(2)若数列{b
n}满足b
n=log
2(a
n+2),设T
n是数列
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286015_ST/0.png)
的前n项和.求证:
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286015_ST/1.png)
.
查看答案
已知椭圆
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286014_ST/0.png)
,过右焦点F且斜率为k(k>0)的直线与C相交于A、B两点,若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286014_ST/1.png)
=
.
查看答案
已知P是抛物线y
2=2x上的一个动点,过点P作圆(x-3)
2+y
2=1的切线,切点分别为M,N,则|MN|的最小值是
.
查看答案
若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286012_ST/0.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286012_ST/1.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286012_ST/2.png)
是平面α内的三点,设平面α的法向量
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286012_ST/3.png)
,则x:y:z=
.
查看答案
若抛物线y=ax
2-1上总存在两点关于直线x+y=0对称,则实数a的取值范围是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286011_ST/0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286011_ST/1.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101231010862528617/SYS201311012310108625286011_ST/2.png)
D.
查看答案