电脑键盘上的字母为何不按顺序排列?请你来做一项统计,下面是一篇小短文,根据短文中字母a,b出现的机会完成后面提出的问题: Two Trips Jack brought a small plane and began to fly it. He soon became excited and made his plane all kinds of tricks. Jack had a friend,named Tom. One day Jack said to him,“I will pick you up in my plane.““I will be glad to."answered Tom. They went up,and Jack flew around for half an hour and did all kinds of tricks in the air. Then they came down. Tom was to be back safely,and said to Jack,“Well,Jack,thank you very much for those two trips in your plane.“Jack was very surprised and asked,“Two trips?““Yes,my first and my last."an-swered Tom. 根据上文填表
出现字母的个数 | 100 | 150 | 200 | 250 | 300 | 350 | 400 | 出现字母a的频数 | | | | | | | | 出现字母a的频率 | | | | | | | | 出现字母b的频数 | | | | | | | | 出现字母b的频率 | | | | | | | |
答案
如图所示:
出现字母的个数 | 100 | 150 | 200 | 250 | 300 | 350 | 400 | 出现字母a的频数 | 12 | 18 | 23 | 28 | 36 | 38 | 45 | 出现字母a的频率 | 0.12 | 0.12 | 0.115 | 0.112 | 0.12 | 0.109 | 0.113 | 出现字母b的频数 | 3 | 3 | 4 | 4 | 6 | 6 | 6 | 出现字母b的频率 | 0.03 | 0.02 | 0.02 | 0.018 | 0.02 | 0.017 | 0.015 |
举一反三
40张牌的牌面朝下,每次抽取一张记下花色放回,洗牌后再抽,抽到红桃、黑桃、方片、梅花的频率依次是20%、25%、30%、20%,则这40张牌中大约有大、小王共______张. | 为配和新课程的实施,某市举行了“应用与创新”知识竞赛,共有1万名学生参加了这次竞赛(满分100分,得分全为整数).为了解本次竞赛成绩情况,从中随机抽取了部分学生的竞赛成绩,进行统计,整理见下表:
组别 | 分组 | 频数 | 频率 | 1 | 49.5~59.5 | 6.0 | 0.12 | 2 | 59.5~69.5 | 120 | 0.24 | 3 | 69.5~79.5 | 180 | 0.36 | 4 | 79.5~89.5 | 130 | c | 5 | 89.5~99.5 | b | 0.02 | 合计 | | a | 1.00 | 已知20个数据如下:28,31,29,33,27,32,29,31,29,27,32,34,29,31,34,33,30,28,32,33,对这些数据编制频率分布表,其中30.5~32.5这一组的频数与频率分别是( )A.5,0.25 | B.4,0.20 | C.6,0.30 | D.6,0.75 |
| 当今,青少年视力水平的下降已引起全社会的关注,为了了解某中学毕业班300名学生的视力情况,从中抽测了一部分学生的视力,进行数据整理如下: (1)在这个问题中,总体是______. (2)填写频率分布表中未完成的部分. (3)若视力4.9,5.0,5.1,5.2均属正常,不需矫正,试估计该毕业班学生视力正常的人数约为多少?分组 | 频数 | 频率 | 3.95~4.25 | 2 | 0.04 | | 6 | 0.12 | 4.55~4.85 | 23 | | 4.85~5.15 | | | 5.15~5.45 | 1 | 0.02 | 合计 | | 1.00 | 从数字1、2、3、…、100这100个连续整数中,任意取一个数,那么这个数能被9整除的频率是______. |
最新试题
热门考点
|
|
|
|