2021年大联盟(Math League)国际夏季四年级数学挑战活动二（含答案）

PAGEPAGE102021美国"大联盟"(MathLeague)国际夏季数学挑战活动2021MathLeagueInternationalSummerChallengeGrade4,SpeedQuestions&Answers1.8000+800+80+8=9000– ?212C)112D)1112Answer:C2.If30ofmy5-dozenpencilsweresharp,howmanyofmypencilswerenotsharp?10203050C3.(2021×1)+(2020×0)=2021+ ?01C)2020D)2021Answer:AofdogsIhaveis6×5morethan6dogs.Ihave?dogs.15243666CIfeverydigitofmysecretcodeisadifferentprimenumber,mysecretcodehasatmost?digits.4567Howmanydigitsdoestheproductoften100shave?342021DIamreadinga300bookin10hours,ataconstantrate.HowmanypageshaveIreadinthepast10minutes?5101530bedividedinto16groupsof4animalscanalsobedividedinto?groupsof8animals.681216BWhatisthesmallestdifferencebetweentwowholenumberswhoseproductis253?21112D)252Answer:CTheperimeterofasquarewithoddside-lengthscouldbe681012DThetime2hoursand2minutesbeforemidnightisA)2:02AMB)10:58PMC)9:58PMD)11:58PMAnswer:CWhichofthefollowingistheproductoftwoprimenumbers?A)100B)112C)120D)142Answer:DFidofetches3outofevery54ballsFlothrows.Atthisrate,howmanyballsmustFlothrowtobesurethatFidofetches54balls?A)18B)162C)972D)2916Answer:CHowmany2-digitmultiplesof15arealsomultiplesof2?0345BAlchewshalfofhisgumeachday.IfAlchews6sticksofgumtoday,howmanysticksofgumdidhechew4daysago?304896D)192Answer:CHowmanywholenumbersarefactorsof2×4×6?56810Answer:DAvaboughtmorethan1newbookfor$6each,andmorethan1usedbookfor$5each.ThetotalcostofherbookscouldbeA)$22B)$23C)$24D)$25Istartedwritingallthemultiplesof2inincreasingorder,startingwith2.Whatwasthe45thdigitIwrote?3579Answer:BWhatisthesumofthedigitsofthegreatest3-digitwholenumberandthedigitsofthesmallest4-digitwholenumber?27283637BAsquarewithperimeter16iscutintotwoidenticalrectangles.Theperimeterofoneofthesetworectanglesis8121624BKaimakes4timesasmanyclocksadayworkingwithafriendasshedoesworkingalone.Kaiandherfriendmake60clocksadaywhentheyworktogether.HowmanyclockscanKaimakein5dayswhensheworksalone?6075C)100D)180Answer:BMyhousenumberdoesnothave2,3,or5asafactor.Whichofthefollowingcouldbemyhousenumber?44556677DTheaverageof5differentwholenumbersgreaterthan0is20.Whatisthegreatestpossiblevalueofoneofthewholenumbers?429096D)100Answer:BBobbought36cupsatacostof4cupsfor$5.Hewillresellthecupsfor$2each.HowmanycupsmustBobselltoearnatleastwhathepaidforall36cups?392223DThepositivemultiplesofawholenumberwerelistedfromleasttogreatest.Ifthe3rdmultiplewas39,the5thmultiplewas134265D)117Answer:CAt65FlavorsIceCreamshop,every65thcustomerwinsfreeicecream.Ifthe50thwinnerwas25customersbeforeme,whatnumbercustomeramI?A)90B)3225C)3250D)3275Answer:DCogcounteddownfrom2021bysubtracting7repeatedly.Howmanypositivemultiplesof3didCogcount?94959697CThereare8rowsofchairs,with18chairsineachrow.Ifwekeepallthechairs,whatisthesmallestnumberofchairswemustmovesothatthenumberofrowsequalsthenumberofchairsineachrow?8183248DSaladdedtwoconsecutiveintegersgreaterthan10.Adding2tothegreaterintegerwouldincreasethetensdigitoftheirsum.Whatisthesmallestpossiblevalueofthesmallerinteger?11144498BTheproductof5differentprimescanbewrittenastheproductofatmost?differentnon-primewholenumbers.2345Answer:B31.Theaverageof2018,2020,2021,2022,and2024isA)5B)2019C)2021D)2022Answer:CThedifferencebetweenanytwooddmultiplesof3isalwaysevenodd36Whatistheprobabilitythat,initsspelling,arandomlychosendayoftheweekusestheletter“s”or“S”?7777Answer:C60seconds=36minutes600minutes6hours1hourAnswer:DStartingwithJanuary,numberthemonthsfrom1to12.Howmanyoftheodd-numberedmonthshaveanoddnumberofdays?1234Answer:DFiveyearsago,AlwasasoldasBobisnow.InhowmanyyearsfromnowwillBobbeasoldasAlisnow?5101520WhenBuckygaveme8coinsworth25¢tohelphimbuildadam,hegavemeexactly1nickel2dimes3nickels5penniesAnswer:D48andintegralsides.Itsperimetercannotbe38425298BThesumof10differentwholenumberscanbe?,butneverless.11455566BTheperimeterofatriangleis36cm.Itslongestsidecouldbe11cm17cm18cm19cmAnswer:BIsaid“nostoneshallgounturned”inmysearchfordifferentwhole-numberfactorsof36.Justhowmanysuchfactorsarethere?68918Answer:CPointsA,B,C,andDlieonaline,butnotinthatorder.IfAB=9,BC=4,andCD=2,theleastpossiblevalueofADis2347Answer:BIfthesymbolhh:mm:ssmeanshours:minutes:seconds,howmuchtimepassesfrom5:55:55P.M.untilmidnight?A)6:04:05B)6:05:05C)7:04:05D)7:05:05Answer:AMultiplythelargest2-digitprimebythesmallest3-digitprime.A)1111B)9191C)9797D)9991Answer:C–whatisthevalueof43?-4412D)-12Answer:B6quarters+2dimes=20pennies+?nickels.25303335BHuckistwiceasoldasBeckyand2yearsolderthanTom.IfBeckyis13,howoldisTom?14202224Answer:DThedifferencebetweentwoprimes,eachgreaterthan100,isalwaysevenoddcompositeprimeHowmanydifferentpositiveprimesarefactorsof2021?2345Ifthesumof4consecutiveoddnumbersis4morethanthesumof4consecutiveevennumbers,thentheleastoftheoddnumbersis?morethantheleastoftheevennumbers.1234Thelargest4-digitintegralmultipleof9equalsthelargest4-digitintegralmultipleofallofthefollowingexcept31117D)101Answer:C(theleastpositiveinteger)–(thelargestnegativeinteger)=210-1greatestcommonfactorof2×4×6×8×10and1×2×3×4×5is248D)120Answer:DWhatmonthwillitbe1000daysafterFebruary14?OctoberNovemberDecemberJanuaryAnswer:BEachsideofatrianglehasadifferentpositiveintegerasitslength.Whatistheleastpossibleperimeterofthistri