二元一次方程组的实际应用-七年级数学

校长为学校学生道路交通安全工作第一责任人，负责校（园）内的道路交通安全管理工作和学生出行的道路交通安全教育，以及学生春(秋)游和其他教育教学活动的道路交通安全管理工作centerpinchecksandanchoringtheinnercylinder.AccordingtoWhilecouplingalignmentshouldkeepoiloutofcavityandlocatetherotoraxisneckraisedarewithintheprescribedlimits,thereshouldbenogaps,Horn,HornandHorn0.05mmfeelergaugesfitinto.Centercoupling,condenserwaterfillingandwater-filledaccordingtofactoryrequirement.ForcouplingthreesupportedrotorCenter,themouthunderthecouplingbetweenthevalueshouldbeasstipulatedinthemanufacturer,usually0.15~0.25mm.Inthecaseofcouplingconnection,ifpossible,liftingonlyonebearingendofthesupportbearingoftherotor,removethebearing,fittedwithspecialtilesandspecialliftingtools,discrotors,checkthejournalfluttertile,shouldgenerallybelessthan0.10MM.Whenthecouplingsandrotorcomeswhenthereisaconflict,thecouplingCentreshallprevail.6.4.5.2.2shaftlookingfor:...6.4.5.3.Provisionalboltconfirmedthepositioningoftherotorsize,aswellasthecouplingbetweentheadjustmentshimthicknessaccuracy,drawingstomeetthetechnicalrequirements.Plane,cylindricalandcleanthecouplingboltholesshouldbecleanandwithoutburrs,scrapironandgrease-free,relativepositionofthecouplingaccordingtothedrawingrequirementsare.Couplingtopscrews,rounddistanceapart,indicatorstomonitormovementoftheaircraft,itsvalueisallowedtopassthevalueaxismoving,mountedadjustmentpads,notepadsinstallationdirectionguidepincouplingwithprocessendclosed.Thebackwheelsslowlytightened,when2mmorso,withstandardwhitebarswheretwobackwheelboltholemeasurementaboveandbelow,confirmtwobackwheelboltholeconcentricity.Then,thesymmetricalhorizontalmounttwotemporaryboltstightened,attentiontomonitordialindicator,theninstallthesymmetricaltemporarybolts,thistimesitesslowlymovingrotor,inthemeasuredcircumferenceof8equalpartsbackwheelrimrock,eachmeasuringrelativechangesinvalueshouldbelessthan0.02mm.6.4.5.4couplingreamedandpairedboltreamingdiereamer,adjustablereamers,boringmill,inseveralways.6.4.5.4.1Generalrequirementsbeforereamingorboring,二元一次方程组的实际应用一、主要知识点回顾1、列方程解应用题的一般步骤:①审题②设未知数③找相等关系④列方程组⑤解方程组⑥检验⑦答题2、列方程解应用题，审题时关键。分清题目中的等量关系，列出相应的方程（组）。注：（1）设未知数时一定要注明____________;（2）列方程（组）时一定要注意统一___________;（3）检验包括判断是否是方程（组）的解和是否符合题意两个方面。3、应用题常见的几种类型：（1）行程问题：①基本量之间的关系：路程＝速度×时间②解题时一般应画线段示意图。（2）工程问题①基本量之间的关系：工作量＝工作效率×工作时间甲、乙合做的工作效率＝甲的工作效率＋乙的工作效率②解题时，若工作总量是抽象的，通常把它设为单位1。（3）浓度问题①基本量之间的关系：溶液＝溶质＋溶剂（指体积或质量）；溶液的浓度＝×100%②解题时应注意配制前后溶液中的不变量和变化量分别是什么？（4）利润问题：①有关量的关系：利润＝售价－进价；利润率＝×100%；利息＝本金×利率×期数②解题时应注意此类问题中的一些关键词语的意义，如“打折”“个人所得税”等等。4、列方程组解应用题，是把“未知”转化为“已知”的重要方法，它的关键是把已知量和未知量联系起来，找出题目中的相等关系。一般来说，有几个未知量就必须列出几个方程，所列方程必须满足：（1）方程两边表示的是同类量；（2）同类量的单位要统一；（3）方程两边所表示的数量要相等。校长为学校学生道路交通安全工作第一责任人，负责校（园）内的道路交通安全管理工作和学生出行的道路交通安全教育，以及学生春(秋)游和其他教育教学活动的道路交通安全管理工作centerpinchecksandanchoringtheinnercylinder.AccordingtoWhilecouplingalignmentshouldkeepoiloutofcavityandlocatetherotoraxisneckraisedarewithintheprescribedlimits,thereshouldbenogaps,Horn,HornandHorn0.05mmfeelergaugesfitinto.Centercoupling,condenserwaterfillingandwater-filledaccordingtofactoryrequirement.ForcouplingthreesupportedrotorCenter,themouthunderthecouplingbetweenthevalueshouldbeasstipulatedinthemanufacturer,usually0.15~0.25mm.Inthecaseofcouplingconnection,ifpossible,liftingonlyonebearingendofthesupportbearingoftherotor,removethebearing,fittedwithspecialtilesandspecialliftingtools,discrotors,checkthejournalfluttertile,shouldgenerallybelessthan0.10MM.Whenthecouplingsandrotorcomeswhenthereisaconflict,thecouplingCentreshallprevail.6.4.5.2.2shaftlookingfor:...6.4.5.3.Provisionalboltconfirmedthepositioningoftherotorsize,aswellasthecouplingbetweentheadjustmentshimthicknessaccuracy,drawingstomeetthetechnicalrequirements.Plane,cylindricalandcleanthecouplingboltholesshouldbecleanandwithoutburrs,scrapironandgrease-free,relativepositionofthecouplingaccordingtothedrawingrequirementsare.Couplingtopscrews,rounddistanceapart,indicatorstomonitormovementoftheaircraft,itsvalueisallowedtopassthevalueaxismoving,mountedadjustmentpads,notepadsinstallationdirectionguidepincouplingwithprocessendclosed.Thebackwheelsslowlytightened,when2mmorso,withstandardwhitebarswheretwobackwheelboltholemeasurementaboveandbelow,confirmtwobackwheelboltholeconcentricity.Then,thesymmetricalhorizontalmounttwotemporaryboltstightened,attentiontomonitordialindicator,theninstallthesymmetricaltemporarybolts,thistimesitesslowlymovingrotor,inthemeasuredcircumferenceof8equalpartsbackwheelrimrock,eachmeasuringrelativechangesinvalueshouldbelessthan0.02mm.6.4.5.4couplingreamedandpairedboltreamingdiereamer,adjustablereamers,boringmill,inseveralways.6.4.5.4.1Generalrequirementsbeforereamingorboring,二、实战。1、班上组织看电影，买了35张票共花去250元，其中甲种位置的票每张8元，乙种票每张6元，问甲、乙两种票各多少张？设甲票x张，乙票y张，列方程组得_______________.2、大数和小数的差为12，这两个数的和为60，则大数是______，小数是______.3、方程组521yxyx的解是（）A.21yxB.12yxC.21yxD.12yx4、某校运动员分组训练，若每组7人，余3人；若每组8人，则缺5人；设运动员人数为x人，组数为y组，则列方程组为（）A.xyxy5837B.xyxy5837C.5837xyxyD.5837xyxy5、在中央电视台2套“开心辞典”节目中，有一期的某道题目是：如图（3）所示，天平中放有苹果、香蕉、砝码，且两个天平都平衡，则一个苹果的重量是一个香蕉的重量的（）A．43倍B．32倍C．2倍D．3倍三、例题分析例题1：（数量的和、差、倍、分问题）2008