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100150200250300350400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
网友回答
解：如图所示：
出现字母的个数100150200250300350400出现字母a的频数12182328363845出现字母a的频率0.120.120.1150.1120.120.1090.113出现字母b的频数3344666出现字母b的频率0.030.020.020.0180.020.0170.015
解析分析：根据频数的概念及频率的计算方法：频率=求解．
点评：本题考查了频数的概念及频率的计算方法．
频数是指每个对象出现的次数．
频率是指每个对象出现的次数与总次数的比值（或者百分比）．即频率=．