数学题的解答，答对给100积分_百度知道
数学题的解答，答对给100积分
甲乙两人以均速绕圆形跑道相向跑步，出发点在圆直径的两端，如果他们同时出发，并在甲跑完60米时第一次相遇，乙跑一圈还差80米时两人第一次相遇，求跑道的长多少米？本妹妹不会做，教教本人吧！
注意注意！！！乙跑一圈还差80米时两人第一次相遇的“第一次”改为“第二次”
提问者采纳
设跑道共长x米，则第一次相遇时甲跑了60米，乙跑了(x/2-60)米,第二次相遇时，甲共跑了（x/2+80）米，乙共跑了（x-80）米，因为他们同时出发，所以相遇时所用时间一致，所以甲乙路程之比即速度之比，而甲乙两人以均速跑，所以两次相遇时甲乙路程之比相等，即
60：（x/2-60）=（x/2+80）：（x-80)
60（x-80）=（x/2-60）（x/2+80）【交叉相乘】
60x - 4800 = x的平方/2 + 10x - 4800
x的平方/4 = 50x
x = 200(/为分数线，数字与括号之间，括号与括号之间省略乘号）所以跑道的长200米。（如理解无误，则检验正确）
提问者评价
其他类似问题
为您推荐：
其他5条回答
解：设跑道长xm,当甲乙相遇时，甲跑了60m，而乙跑了（x-80）m，
因为出发点在圆直径的两端，所以60-（x-80）=0.5x或（x-80）-60=0.5x，
解得x=280÷3或x=280，经检验均成立
(60+80)×2=280(米)跑道长280米红线是相遇点
80-60=20m20*2=40m
数学题的相关知识
等待您来回答
下载知道APP
随时随地咨询
出门在外也不愁请尽快解决！100积分_百度知道
实在不会，你就直接写他多久干一次啥，干啥咋样，多用宾语后置....语法
My classmate, Maggie, hardly ever does housework. She does her homework three hours every day. Once a month she has a picnic. She hardly watches TV. But she surfs the internet once a week. Every day she does some reading. She has sports often. She exercises five times a week and goes to the movies once a month.
Whte is fuck
其他类似问题
为您推荐：
等待您来回答
下载知道APP
随时随地咨询
出门在外也不愁初中被动语态语法快啊,100个积分了.回答要多!_百度作业帮
初中被动语态语法快啊,100个积分了.回答要多!
初中被动语态语法快啊,100个积分了.回答要多!
本资料摘自奥风英语《中考语法完全突破记忆大纲》中动词的时态和语态一讲：二、动词的语态语态即表示句子中主谓关系的一种动词形式.分为主动语态和被动语态.1.被动语态的使用① 不知道或没必要指出动作的发出者时.如：Gunpowder was invented in China.火药是中国发明的.The singer is not thought highly of.那个歌星受到的评价不高.② 需要突出或强调动作的承受者时.如：The boy was poorly treated.那个男孩受到虐待.Four people were killed in the accident.2.被动语态的基本结构：主语+be +过去分词(+by+动作的发出者）① 一般现在时：am/is/are+过去分词如：Trees are planted every year.② 现在进行时 am/is/are+ being +过去分词如：The road is being repaired.③ 现在完成时 have/has + been +过去分词如：The work has been finished.④ 一般过去时 was/were + 过去分词如：The story was told by him.Many birds were killed last year.⑤过去进行时 was/were+ being + 过去分词如：The new house was being painted when I got home.⑥过去完成时 had +been+ 过去分词如：He told me that the work had been finished.⑦一般将来时 will +be + 过去分词如：The problem will be discussed tomorrow.⑧ 过去将来时 would/should +be +过去分词如：He said that the Christmas tree would be put up soon.⑨情态动词的被动语态情态动词+ be +过去分词 如：The problem must be solved soon.Children should be taught to love animals.3.被动语态注意事项① 只有及物动词,或是“不及物动词+介词”构成的短语才能用被动语态.不及物动词,连系动词不能接宾语,故不能用被动语态.如：Cotton feels soft.The roses smell sweet.② 常考的没有被动语态的词语happen/take place 发生,break out (战争,火灾等)突然爆发,发生如：Great changes have taken place in my hometown since 1990.③ 在感官动词（feel,see,hear,watch,listen to,look at,notice,observe等）.和使役动词（make）后作宾补时不定式的to要省掉,而变为被动语态,即作主补时要加上to.如：We saw a man walk across the street.A man was seen to walk across the street.④ 注意在将“不及物动词+(……)+介词”结构的主动语态变为被动语态时,不可露掉介词.如：The old lady is being taken good care of .4.常见主动表被动的用法①.在主语是物的句子中,sell,read,write,run等词常用主动表被动.如：The book sells well.这本书卖的很好.This pen writes smoothly.这支笔很好用.Your composition reads well.②.物作主语时,need/want +doing表被动.=need/want +to be done.如：The blackboard needs cleaning (to be cleaned.) 黑板需要擦了.③.作定语用的不定式,当其逻辑主语是句中主语或宾语时,用主动表被动.如：I have a lot of work to do.I will give you some books to read.④.主语+ be +形容词（easy,difficult,necessary…）+to do结构中,常用主动表被动.如：This telephone number is easy to remember.
初中被动语态语法讲解(一) 语 态 分 类英语动词有两种语态.，主动语态和被动语态。主动语态表示主语是动作的执行者，被动语态表示主语是动作的承受者。如：
They will build a new bridge over the river. (主动)A new bridge will be built over the river. (被动)汉...百度文库-信息提示
两大类热门资源免费畅读
续费一年阅读会员，立省24元！
信息提示对不起，该文档已被删除，无法查看
4秒后，自动返回首页}