某校从参加高二年级学业水平测试的学生中抽出100名学生，其数学成绩的频率分布直方图如图所示．其中成绩分组区间是[40，50），[50,60），[60,70），[70,80）， [80,90) ,[90

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某校从参加高二年级学业水平测试的学生中抽出100名学生，其数学成绩的频率分布直方图如图所示．其中成绩分组区间是[40，50），[50,60），[60,70），[70,80）， [80,90) ,[90,100]．则成绩在[80 ,100]上的人数为

A：70

B：60

C：35

D：30

上一题下一题 0.0难度选择题更新时间:2012-05-07 01:24:59

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D

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What are some of the steps a person can take to prevent his house from being broken in while he or she is away? One step is to make sure that the house has a live-in look. Living room shades could be pulled down only half-away. Bedrooms that usually have the shades pulled down at night should be left down. Another is to make sure that all outside looks are the dead-belt(带) type. Still another is to leave several low-watt(瓦) lights burning and make sure that one is in the kitchen. Lights that turn on and off automatically(自动地) are the best. Then, too, it is a good idea to leave a radio turned into a talking station. Any type of conversation makes a burglar(盗贼) think twice before trying to enter. Finally, while away on vacation, make sure that nothing collected in the front or back of the house. Make certain that the newspaper is stopped and that a trusted neighbor has been asked to pick up the posts.

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