2021年大聯(lián)盟(Math League)國際夏季五年級數(shù)學挑戰(zhàn)活動二（含答案）

112021美國"大聯(lián)盟"(MathLeague)國際夏季數(shù)學挑戰(zhàn)活動2021MathLeagueInternationalSummerChallengeGrade5,SpeedQuestions&Answers1.(2021÷5)+(2021÷5)+(2021÷5)+(2021÷5)+(2021÷5) =A)2020 B)2021 C)2022 D)8084Answer:BKirokthedragonhas2021scalesonhisneck,3031scalesonhiswings,and5051scalesontherestofhisbody.WhatisthetotalnumberofscalesonKirok’sbody?A)1013 B)7073 C)10103 D)100103Answer:CWhatistheremainderwhen(7+77+777+7777)isdividedby7?A)0 B)1 C)4 D)1234Answer:AFouroutofeveryfivedentistsrecommendHiGlotoothpaste.IfIask100dentistswhethertheywouldrecommendHiGlotoothpaste,howmanyofthedentistswillrecommendit?PAGEPAGE10A)25 B)30 C)50 D)80Answer:DWhatistheperimeterofasquarethathasanareaof64?A)16 B)24 C)32 D)64Answer:C6.4×5×101=1010×?A)2 B)20 C)101 D)1010Answer:AEachangleofarectangleis?degreesgreaterthaneachangleofanequilateraltriangle.A)30° B)60° C)90° D)120°Answer:AItis2021hoursaftermidnight.Whattimeisit?A)5AM B)7AM C)5PM D)7PMAnswer:AIf20%ofanumberis50,whatis40%ofthesamenumber?A)30 B)60 C)100 D)150Answer:CAsherides,SirReginaldvonPrimeisgoingtoplantaflageverytimethetotaldistancehehasriddenisaprimenumberofkm.Howfarwillhehavegonewhenheplantshis11thflag?A)23km B)29km C)31km D)37kmAnswer:CThegreatestcommonfactorof43×52and53×72isA)5 B)52 C)53 D)55Answer:BHowmany2-digitoddnumbersdonothave3aseitherdigit?A)32 B)36 C)40 D)44Answer:AMyaveragescoreonthe3testsI’vetakensofaris85.WhatscoredoIhavetogetonthenexttoraisemyaveragescoreto88?A)94 B)95 C)96 D)97Answer:DNanknitsnewtopsfornewborns.Todaysheknittedonemoretopthanyesterday.ThenumberoftopssheknittedinthetwodayscombinedcouldbeA)12 B)23 C)34 D)100Answer:B8dozensocks=?pairsofsocksA)24 B)36 C)48 D)96Answer:CAboyisinlinewith30peoplebehindhimandtwiceasmanyaheadofhim.Howmanypeopleareinthisline?A)60 B)61 C)90 D)91Answer:DIfthesumof6consecutiveintegersis255,whatisthesumofthegreatestandtheleastoftheintegers?A)38 B)43 C)81 D)85Answer:DPaolaranthe300mfromherdoortothebusin20seconds.Whatwasherspeedinkm/hr?A)15 B)20 C)34 D)54Answer:DWhatistheproductofallthepositivedivisorsof64?A)64 B)8×642 C)8×643 D)644Answer:Cdouble,mysister’sagewilltriple,andmybrother’sagewillquadruple!Whatisthesumofouragesnow?A)32.5 B)55 C)90 D)100.5Answer:BThegreatestprimefactorofthenumberofsecondsin2197hoursisA)11 B)13 C)17 D)19Answer:BInthecountryofLatka,6simkasareworth25ibidasand2ibidasareworth15yatabes,IfIpay12simkasforachickenthatispricedat365yatabes,howmanyyatabesshouldIexpectinchange?A)10 B)12 C)13 D)15Answer:AAlighthousecanbeseenfromatmost50kmonaclearnightbutfromatmost20kmduringfog.Thegreatestviewingdistanceonaclearnightiswhatpercentofthegreatestduringfog?A)40 B)60 C)150 D)250Answer:DWhatisthegreatestpossiblenumberofpointsofintersectionsofacircleandarectangle?A)2 B)4 C)6 D)8Answer:DHowmanysquaresofintegershave3digits?A)20 B)21 C)22 D)23Answer:CAlwritesthefirst20%ofhisreportonMonday,then30%oftheremainingreportonTuesday.WhatpercentoftheentirereportthatAlbeganonMondayremainstobewrittenonWednesday?A)44% B)50% C)54% D)56%Answer:D27.42×44×46×48=A)240 B)41024 C)1630 D)6430Answer:AZakshuffledtogetherfourdecksofcardsandstarteddealingthemout.Surprisingly,thesuitscameoutinapatternthatrepeatedasfollowsuntilthe26thclubappeared:club,diamond,heart,club,heart,diamond,club,diamond,heart,club,heart,diamond,HowmanycardsmustZakdealinordertohavedealt26oftheclubsuit?A)75 B)76 C)78 D)84Answer:BMylocalicecreamshopoffers15differentflavorsoficecream.IfIwanttwoscoopsoficecream,eachscoopadifferentflavor,howmanycombinationsoftwoscoopsoficecreamarepossible?A)29 B)30 C)105 D)210Answer:CInezmultiplied21bytheproductof2121s.Thenshesubtracted21fromthattimes.Withwhatnumberdidsheendup?A)0 B)2120 C)2121+212 D)2122–212Answer:AWhatisthegreatestnumberofprimefactors(notnecessarilyalldifferent)thatathree-digitnumbercanhave?A)5 B)6 C)8 D)9Answer:DHowmanyofthefirst2021evenpositiveintegersaredivisibleby6?A)336 B)337 C)673 D)674Answer:CMaestromustbeabletodividethebirdsinhisall-birdchoirinto6,7,and8equalwantsa3-digittotalnumberofbirds.Inall,howmanysuch3-digitnumbersarepossible?A)2 B)3 C)4 D)5Answer:DIf25peopletake27hourstocatchallthebirds,atthatratehowlongwouldittake45peopletocatchallthebirds?A)9hrs B)15hrs C)18hrs D)21hrsAnswer:BWhatistheleastnumberofconsecutivepositiveintegersstartingwith1thatmustbemultipliedtogethertogetamultipleof2021?A)22B)80C)90D)105Answer:C(2+4+8)2=A)(3+4+5)2(4+5+6)×2(1+2+4)2×4D)22+42+82Answer:CEachequilateraltriangleshownhasaperimeterof9.Whatistheperimeterofthefigure?A)6 B)8 C)10 D)12Answer:DThebaseofanisoscelestrianglewithintegralsidesis12.Whatcouldbetheperimeter?A)20 B)22 C)24 D)26Answer:DEmmacountedupfrom0by1severysecondfor5minutes,andthendownby1severysecondfor2minutes.Whatnumberdidsheendon?A)180 B)240 C)360 D)480Answer:AWhatisthe200thnumberinthesequence1,1,1,2,1,3,1,4,1,5,...?A)1 B)100 C)101 D)200Answer:B2020isdivisibleby?differentprimenumbers.A)2 B)3 C)4 D)5Answer:BThelargeranglebetweentheminutehandandthehourhandofacircularclockat1:10PMmeasuresA)300° B)315° C)330° D)335°Answer:DHowmanyprimenumberslessthan50havereciprocalsthatareterminatingdecimals?A)1 B)2 C)3 D)4Answer:BRedpensaresoldat3for$1andblackpensaresoldat4for$1.50.Alicebought12redpensand24blackpens.Shepaidforthemwitha$20bill.Howmuchchangedidshereceive?A)$7 B)$9 C)$13 D)$16Answer:AThenumber1000hasonly16positivewholenumberfactors.Theproductofall16ofthesefactorsisA)108 B)1016 C)1024 D)1032Answer:CTheaverageof21consecutiveintegersis31.ThelargestoftheseintegersmustbeA)40 B)41 C)51 D)52Answer:B47.(221×1000)+(221×100)+(221×10)+(221×1)isdivisiblebyA)2 B)3 C)4 D)11Answer:D48.314159272–314159262=31415926+?A)0 B)31415927 C)31415928 D)31415925Answer:BEachkmofa5kmrace,myhorse’saveragespeeddecreased1km/hr.IfIaveraged5km/hratfirst,ittookme?minutestofinish.A)120 B)137 C)216 D)685Answer:BImakeastraightcutthrougharectangularpieceofpaperandgettwopieces.WhenImakeastraightcutthroughoneofthesetwopieces,Ithenhavethreepieces.Altogether,thenumberofedgesonthesethreepiecescannotbeA)8 B)9 C)10 D)11Answer:A51.

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17 D)noneofthese154Answer:AA)4 B)25 C)50 D)100Answer:CIfthetotalvalueofanequalnumberofpennies,nickels,anddimesis$3.20,whatisthevalueofthenickelsalone?A)40cents B)60cents C)80cents D)100centsAnswer:DWhatistheonesdigitof22021?A)2 B)4 C)6 D)8Answer:AThesumof50consecutivewholenumbersequalsthesumof25otherconsecutivewholenumbers.Ifthesmallestofthe50numbersis2021,thesmallestofthe25numbersisA)4079 B)4103 C)2021 D)2070Answer:AIf