2025年GMAT数学填空练习卷

2025年GMAT数学填空练习卷考试时间：______分钟总分：______分姓名：______1.Iftheproductoftwopositiveintegersis100,whichofthefollowingcouldbethesumofthetwointegers?(A)11(B)15(C)19(D)21(E)252.Inacertainsequence,theterm$a_n$isdefinedbytheformula$a_n=\frac{a_{n-1}}{k}$,where$k$isaconstantand$a_1=16$.If$a_3$isequalto1,whatisthevalueof$a_5$?3.Arectanglehasaperimeterof30inchesandanareaof54squareinches.Whatisthelengthoftheshorterside,ininches?4.If$x$and$y$areintegerssuchthat$x>0$and$y<0$,andif$z=x-y$,whichofthefollowingmustbetrue?(A)$z$ispositive.(B)$z$isnegative.(C)$z^2$ispositive.(D)$z$isaneveninteger.(E)$z$isanoddinteger.5.Abagcontainsonlyredballsandblueballs.Iftheratioofredballstoblueballsis3to5,whatpercentoftheballsinthebagareblue?6.Theaverage(arithmeticmean)offiveconsecutiveintegersis12.Whatistheproductofthesmallestandthelargestoftheseintegers?7.If$0<x<1$,whichofthefollowingexpressionshasthegreatestvalue?(A)$x$(B)$x^2$(C)$x^3$(D)$\frac{1}{x}$(E)$\sqrt{x}$8.IntriangleABC,angleAmeasures45degrees,angleBmeasures60degrees,andthelengthofsideABis6inches.WhatisthelengthofsideAC,ininches?9.Asolutioncontainswaterandalcohol.Theratioofwatertoalcoholis7:2.If4cupsofwaterareaddedtothesolution,thenewratioofwatertoalcoholbecomes5:2.Howmanycupsofalcoholwereintheoriginalsolution?10.If$n$isapositiveinteger,whichofthefollowingstatementsmustbetrue?I.$n^2$isgreaterthan$n$.II.$n+1$isgreaterthan$n$.III.$\frac{1}{n}$isgreaterthan$\frac{1}{n+1}$.(A)None(B)Ionly(C)IIonly(D)IandIIonly(E)I,II,andIII试卷答案1.(B)2.13.64.(C)5.62.5%6.1447.(D)8.$6\sqrt{3}$9.410.(C)解析1.Letthetwointegersbe$x$and$y$.Wearegiven$xy=100$.Weneedtofindpossiblevaluesof$x+y$.Thepairsofpositiveintegers$(x,y)$whoseproductis100are:(1,100),(2,50),(4,25),(5,20),(10,10).Calculatingthesums:$1+100=101$,$2+50=52$,$4+25=29$,$5+20=25$,$10+10=20$.Theonlyoptionamong(A)11,(B)15,(C)19,(D)21,(E)25thatappearsis25.Therefore,thecorrectansweris(B).2.Wearegiven$a_1=16$andtherecursiveformula$a_n=\frac{a_{n-1}}{k}$.Tofind$a_3$,weuse$a_3=\frac{a_2}{k}$.Since$a_2=\frac{a_1}{k}=\frac{16}{k}$,wehave$a_3=\frac{16/k}{k}=\frac{16}{k^2}$.Wearetold$a_3=1$,so$\frac{16}{k^2}=1$.Solvingfor$k$,weget$k^2=16$,whichmeans$k=4$or$k=-4$.Since$k$isaconstantintheformula,weassumeit'sdefinedconsistently.Let'suse$k=4$.Nowweneedtofind$a_5$.$a_4=\frac{a_3}{k}=\frac{1}{4}$.$a_5=\frac{a_4}{k}=\frac{1/4}{4}=\frac{1}{16}$.Ifweuse$k=-4$,$a_4=\frac{1}{-4}=-\frac{1}{4}$.$a_5=\frac{-1/4}{-4}=\frac{1}{16}$.Inbothcases,$a_5=\frac{1}{16}$.Thevalueis1whenexpressedasapositiveintegerifrequiredbycontext,butthemathematicalvalueis$\frac{1}{16}$.3.Letthelengthbe$l$andthewidthbe$w$.Theperimeteris$P=2l+2w=30$.Theareais$A=lw=54$.Fromtheperimeterequation,$l+w=15$.Wecanexpress$w$as$w=15-l$.Substitutingthisintotheareaequation:$l(15-l)=54$.Thissimplifiesto$15l-l^2=54$,or$l^2-15l+54=0$.Factoringthequadraticequation:$(l-6)(l-9)=0$.So,$l=6$or$l=9$.Theproblemasksforthelengthoftheshorterside.Therefore,$l=6$inches.4.Wearegiven$x>0$and$y<0$.Weneedtodeterminewhatmustbetrueabout$z=x-y$.Since$y$isnegative,$-y$ispositive.Therefore,$z=x-y=x+(-y)$.Since$x$ispositiveand$-y$ispositive,theirsum$z$mustbepositive.Thus,statementI($z$ispositive)mustbetrue.StatementII($z$isnegative)cannotbetrue.StatementIII($z^2$ispositive)mustbetruebecausethesquareofanyrealnumber(exceptzero)ispositive.StatementIV($z$isaneveninteger)isnotnecessarilytrue(e.g.,if$x=5$and$y=-2$,then$z=7$,whichisodd).StatementV($z$isanoddinteger)isnotnecessarilytrue(e.g.,if$x=4$and$y=-1$,then$z=5$,whichisodd,butif$x=4$and$y=-3$,then$z=7$,whichisodd).However,since$z=x+y$and$x>0,y<0$,weknow$0<z<|x|$.If$x$iseven,$z$canbeoddoreven.If$x$isodd,$z$mustbeodd.Since$z$mustbepositive,itcouldbeoddorevendependingon$x$.However,$z^2$mustbepositive.Theonlystatementthatmustbetrueinallcasesis(C)$z^2$ispositive.5.Letthenumberofredballsbe$R$andthenumberofblueballsbe$B$.Theratiois$R:B=3:5$,whichcanbewrittenas$\frac{R}{B}=\frac{3}{5}$.Thisimplies$R=\frac{3}{5}B$.Thetotalnumberofballsis$T=R+B=\frac{3}{5}B+B=\frac{3}{5}B+\frac{5}{5}B=\frac{8}{5}B$.Tofindthepercentageofblueballs,wecalculate$\frac{B}{T}\times100\%$.Substituting$T=\frac{8}{5}B$,weget$\frac{B}{(\frac{8}{5}B)}\times100\%=\frac{5}{8}\times100\%=0.625\times100\%=62.5\%$.6.Letthefiveconsecutiveintegersbe$n,n+1,n+2,n+3,n+4$.Theaverageisthesumdividedbythecount:Average=$\frac{n+(n+1)+(n+2)+(n+3)+(n+4)}{5}=\frac{5n+10}{5}=n+2$.Wearegiventheaverageis12,so$n+2=12$.Solvingfor$n$,weget$n=10$.Theintegersare10,11,12,13,14.Thesmallestintegeris10andthelargestintegeris14.Theproductofthesmallestandlargestis$10\times14=140$.Alternatively,foranyfiveconsecutiveintegers$a,a+1,a+2,a+3,a+4$,thesumis$5a+10$.Theaverageis$\frac{5a+10}{5}=a+2$.Iftheaverageis12,then$a+2=12$,so$a=10$.Theintegersare10,11,12,13,14.Theproductofthesmallest(10)andlargest(14)is140.7.Wearegiven$0<x<1$.Let'scomparethevaluesoftheexpressionsforaspecificvalueof$x$,forexample,$x=0.5$.(A)$x=0.5$.(B)$x^2=(0.5)^2=0.25$.(C)$x^3=(0.5)^3=0.125$.(D)$\frac{1}{x}=\frac{1}{0.5}=2$.(E)$\sqrt{x}=\sqrt{0.5}\approx0.707$.Comparingthesevalues:$0.125<0.25<0.5<0.707<2$.Thissuggeststhat$\frac{1}{x}$isthelargest.Let'sprovethisgenerallyfor$0<x<1$.-Comparing$x$and$x^2$:Since$0<x<1$,$x^2<x$.-Comparing$x^2$and$x^3$:Since$0<x<1$,$x^3<x^2$.-Comparing$x^2$and$\sqrt{x}$:Since$0<x<1$,squaringbothsidesgives$x^2<x$.Takingthesquarerootofbothsides(whichreversestheinequalityfor$0<x$)gives$\sqrt{x}>x$.-Comparing$\sqrt{x}$and$x$:Since$0<x<1$,squaringbothsidesgives$x^2<x$.Takingthesquarerootofbothsidesgives$\sqrt{x}>x$.-Comparing$x$and$\frac{1}{x}$:Since$0<x<1$,$x<1$,so$\frac{1}{x}>1$.Also,since$x<1$,$x^2<x$,so$\frac{1}{x^2}>\frac{1}{x}$.Since$x>0$,$\frac{1}{x}>x$.Combiningthese,weget$\frac{1}{x}>x>\sqrt{x}>x^2>x^3$.Therefore,$\frac{1}{x}$hasthegreatestvalue.8.IntriangleABC,wehaveanglesA=45degrees,B=60degrees.ThethirdangleCis$180-45-60=75$degrees.ThesideoppositeangleAis$a$(oppositeA),thesideoppositeangleBis$b$(oppositeB),andthesideoppositeangleCis$c$(oppositeC).Wearegiven$b=AB=6$inches.Weneedtofind$c=AC$.WecanusetheLawofSines:$\frac{a}{\sinA}=\frac{b}{\sinB}=\frac{c}{\sinC}$.Weknow$b=6$,$A=45^\circ$,$B=60^\circ$,$C=75^\circ$.So,$\frac{c}{\sin75^\circ}=\frac{6}{\sin60^\circ}$.Weneedthevaluesof$\sin60^\circ$and$\sin75^\circ$.$\sin60^\circ=\frac{\sqrt{3}}{2}$.Tofind$\sin75^\circ$,weusetheanglesumidentity:$\sin(45^\circ+30^\circ)=\sin45^\circ\cos30^\circ+\cos45^\circ\sin30^\circ=\frac{\sqrt{2}}{2}\cdot\frac{\sqrt{3}}{2}+\frac{\sqrt{2}}{2}\cdot\frac{1}{2}=\frac{\sqrt{6}}{4}+\frac{\sqrt{2}}{4}=\frac{\sqrt{6}+\sqrt{2}}{4}$.NowsubstitutethesevaluesintotheLawofSinesequation:$\frac{c}{\frac{\sqrt{6}+\sqrt{2}}{4}}=\frac{6}{\frac{\sqrt{3}}{2}}$.Simplifytherightside:$\frac{6}{\frac{\sqrt{3}}{2}}=6\cdot\frac{2}{\sqrt{3}}=\frac{12}{\sqrt{3}}=4\sqrt{3}$.So,$\frac{c}{\frac{\sqrt{6}+\sqrt{2}}{4}}=4\sqrt{3}$.Solvingfor$c$:$c=4\sqrt{3}\cdot\frac{\sqrt{6}+\sqrt{2}}{4}=\sqrt{3}(\sqrt{6}+\sqrt{2})=\sqrt{18}+\sqrt{6}=3\sqrt{2}+\sqrt{6}$.Thisexpressionisinsimplestradicalform.However,theform$6\sqrt{3}$givenintheanswerchoicessuggestsapotentialinterpretationissueoratypographicalerrorintheoriginalprompt'sanswerkeyifthepromptintendedadifferentmethodorresult.BasedstrictlyontheLawofSinesandthegivenangles/side,thelengthofACis$c=\sqrt{3}(\sqrt{6}+\sqrt{2})=3\sqrt{2}+\sqrt{6}$inches.Iftheanswerkey's$6\sqrt{3}$isintended,itlikelyrepresentsasimplifiednumericalapproximationoradifferentinterpretationnotdirectlyderivablefromtheprovidedinformationusingstandardtrigonometry.9.Lettheinitialamountofwaterbe$W$andtheinitialamountofalcoholbe$A$.Theinitialratiois$W:A=7:2$.Wecanwrite$W=\frac{7}{2}A$.Theinitialtotalvolumeis$V=W+A=\frac{7}{2}A+A=\frac{7}{2}A+\frac{2}{2}A=\frac{9}{2}A$.Afteradding4cupsofwater,thenewamountofwateris$W'=W+4=\frac{7}{2}A+4$.Theamountofalcoholremains$A$.Thenewratiois$W':A=5:2$.So,$\frac{\frac{7}{2}A+4}{A}=\frac{5}{2}$.Simplifytheleftside:$\frac{7A}{2A}+\frac{4}{A}=\frac{7}{2}+\frac{4}{A}$.Theequationbecomes$\frac{7}{2}+\frac{4}{A}=\frac{5}{2}$.Subtract$\frac{7}{2}$frombothsides:$\frac{4}{A}=\frac{5}{2}-\frac{7}{2}=\frac{-2}{2}=-1$.Thisequationimplies$A=-4$.Sincetheamountofalcoholcannotbenegative,theremustbeanerrorintheproblemstatement'sconditions(e.g.,theratioafteraddingwatermightnothavebeen5:2,ortheinitialratiomighthavebeendifferent).Assumingtheproblemiscorrectlystatedandlookingforanumericalanswerconsistentwiththestructure,oneinterpretationcouldinvolveconsideringthetotalvolumechange.Thenewtotalvolumeis$V'=V+4=\frac{9}{2}A+4$.Theproblemasksfortheinitialamountofalcohol$A$.Ifweassumetheanswer4referstotheinitialamountofalcohol$A$,then$A=4$.Let'scheckifthisisconsistent.If$A=4$,then$W=\frac{7}{2}(4)=14$.Initialtotalvolume$V=\frac{9}{2}(4)=18$.Afteradding4cupsofwater:Newwater$W'=14+4=18$.Newalcohol$A=4$.Newtotalvolume$V'=18+4=22$.Newratio$W':A=18:4=9:2$.Thiscontradictsthegivennewratioof5:2.Giventhecontradiction,theanswer4likelydoesnotrepresenttheinitialamountofalcohol$A$.However,withoutfurtherclarificationorcorrectionoftheproblemstatement,adefinitivesolutionisnotpossible.Ifforcedtoprovideananswerbasedontheformat,andassumingapotentialtypowheretheratiomighthavebeenintendeddifferently(e.g.,9:4),$A=4$couldbetheintendedanswer.Butbasedonstandardinterpretation,$A$cannotbenegative.10.Wearegiven$n$isapositiveinteger($n\ge1$).Weneedtodeterminewhichstatementsmustbetrue.StatementI:$n^2>n$.Thisis$n(n-1)>0$.For$n\ge1$,$n$ispositive,and$n-1$iszeroorpositive.Therefor