SAT数学词汇记忆技巧汇总

官方网站：:Themarkedangle,ABCmustbemorethan90degreesbecauseitistheexternalangleoftriangleBDC,andmustbeequaltothesumofanglesBDC(90)andDCB.AlsoABCisnotastraightlineandmustbelessthan180.Therefore905x180Theonlyvalueofxwhichsatisfiesthisrelationis20.2.CorrectAnswer:AExplanation:20largecakeswillrequiretheequivalentof10helpersworkingforonehour.700smallcakeswillrequiretheequivalentof20helpersworkingforonehour.Thismeansifonlyonehourwereavailablewewouldneed30helpers.Butsincethreehoursareavailablewecanuse10helpers.3.CorrectAnswer:EExplanation:Indianstampsarecommontobothratios.MultiplybothratiosbyfactorssuchthattheIndianstampsarerepresentedbythesamenumber.US:Indian=5:2,andIndian:British=5:1.Multiplythefirstby5,andthesecondby2.NowUS:Indian=25:10,andIndian:British=10:2HencethetworatioscanbecombinedandUS:British=25:24.CorrectAnswer:CExplanation:Drawthediagram.Thediagonaloftherectangleisthediameterofthecircle.Thediagonalisthehypotenuseofa3,4,5triangle,andistherefore,5.Circumference=π.diameter=5π官方网站：:Iftwosetsoffourconsecutiveintegershaveoneintegerincommon,thetotalinthecombinedsetis7.,andwecanwritethesetsasn+(n+1)+(n+2)+(n+3)and(n+3)+(n+4)+(n+5)+(n+6)Notethateachterminthesecondsetis3morethantheequivalentterminthefirstset.Sincetherearefourtermsthetotalofthedifferenceswillbe4x3=126.CorrectAnswer:DExplanation:Youcansolvethisbybacksolving–substitutetheanswerchoicesintheexpressionandseewhichgivesthegreatestvalue.satA(-1+2)/(-1-2)=-2/2=-1;B(0+2)/(0-2)=2/-2=-1;C(1+2)/(1-2)=3/-1=-3;D(3+2)/(3-2)=5/1=5;E(4+2)/(4-2)=6/2=3Ifyouhadjustchosenthelargestvalueforxyouwouldhavebeenwrong.Soalthoughitlooksalongmethod,itisactuallyquickandaccuratesincethenumbersarereallysimpleandyoucandothemathinyourhead.7.CorrectAnswer:DExplanation:(Totalareaofsquare-sumoftheareasoftrianglesADEandDCF)willgivetheareaofthequadrilateral9-(2x½x3x1.5)=4.58.CorrectAnswer:E官方网站：:IncaseI,ifnis-1,then2nislessthann.IncaseII,ifnisafractionsuchas½thenn2willbelessthann.IncaseIII,ifnis2,then2-n=0,whichislessthann.Therefore,noneofthechoicesmustbegreaterthann9.CorrectAnswer:CExplanation:Ifaftereachbounceitreaches2/5ofthepreviousheight,thenafterthesecondbounceitwillreach2/5x125.Afterthethirditwillreach2/5x2/5x125.Afterthefourthitwillreach2/5x2/5x2/5x125.Thiscancelsdownto2x2x2=810.CorrectAnswer:AExplanation:Thesmallestvaluefornsuchthat5nisasquareis5.75npcannowbewrittenas75x5xp.Thisgivesprimefactors....3x5x5x5xpTomaketheexpressionaperfectcube,pwillhavetohavefactors3x3,andhencep=9n+p=5+9=14