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!Probability

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Question1: Theohas3redsweetsand2whitesweets. Hepicksasweetatrandom.

(a)WritedowntheprobabilitythatTheopicksaredsweet.

(b)WritedowntheprobabilitythatTheopicksawhitesweet.

Question2: Leahhas12cards,eachwithashapeonit. Shetakesacardatrandom.

(a)WhatistheprobabilitythatLeahtakesacardwithastaronit?

(b)WhatistheprobabilitythatLeahtakesacardwithatriangleonit?

(c)WhatistheprobabilitythatLeahtakesacardwithacircleonit?

Question3: Ralphhas9cards,eachwithanumberonit.

Hepicksacardatrandom. Writedowntheprobabilitythatthechosencardis

(a)thenumber8 (b)anevennumber (c)anumberlessthan7

(d)amultipleof4 (e)asquarenumber (f)aprimenumber

Question4: Thereare12redroses,5yellowrosesand3whiterosesinavase. Felixtakesarose,atrandom,fromthevase.

(a)Writedowntheprobabilitythathetakesawhiterose.(b)Writedowntheprobabilitythathetakesaredorawhiterose.(c)WritedowntheprobabilitythatFelixtakesarosethatisnotred.

Examples

Workout

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!Probability

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Question5: Leonthrowsabiasedcoin. Theprobabilityofgettingtailsis0.4 Workouttheprobabilityofgettingheads.

Question6: Edithplantsadaffodilbulb. Theprobabilitythatthebulbwillgrowis0.8 Whatistheprobabilitythatthebulbwillnotgrow?

Question7: WycombeWanderersplayamatchoffootball. Theprobabilitythattheywinthematchis0.28 Theprobabilitythattheydrawthematchis0.55 Workouttheprobabilitythattheylosethematch.Question8: Evelynhas80pensinadrawer. 15pensareblackandtheotherpensareblue.

Evelynpicksapenatrandomfromthedrawer.

(a)WhatistheprobabilitythatEvelynpicksablackpen? (b)WhatistheprobabilitythatEvelynpicksabluepen?

Question9: Thereare20countersinabag.

2ofthecountersarewhite. 1ofthecountersispink. 4ofthecountersareblack. Therestofthecountersarepurple.

Cartertakesacounteratrandomfromthebag. Showthattheprobabilitythatthecounteriswhiteorpurpleis�

Question10: Thereareonlypink,yellow,greenandbluecountersinabag. Thetableshowstheprobabilitythatacountertakenatrandomfromthebag willbepink,greenorblue.

(a)Workouttheprobabilitythatthecountertakenisyellow

Thereare40countersinthebag.

(b)Workoutthenumberofbluecountersinthebag.

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Question11: Darcyhasabiasedspinner. Aspinnerhassectionslabelled1,2,3,4and5. Thetablebelowshowsinformationaboutsomeoftheprobabilities

Workoutthevalueofx.

Question12: FrederickorganisesarafYleforhisschoolfayre. Thetopprizeisarideinahotairballoon,whichwillbewonby1ticket. AltogetherFredericksells700rafYletickets. MissRobinsonbuys5ticketsfortherafYle. WorkouttheprobabilitythatMissRobinsondoesnotwin.

Question13: Thereare20sweetsinabox.Theprobabilitythatachocolateispickedatrandomfromtheboxis0.6 Howmanychocolatesareinthebox?

Question14: Abagcontains600colouredcounters. Thecountersareyellow,brownororange. Thereare117yellowcountersinthebag. Theprobabilitythatabrowncounterischosenfromthebagis0.35 Calculatethenumberoforangecountersinthebag.

�

Question1: Meganhasafair6sidedspinner. ThespinnerhasthelettersA,BandConit.

TheprobabilitythatthespinnerwilllandonanAis�

TheprobabilitythatthespinnerwilllandonaCis� Writethelettersonthespinner.

Apply

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Question2: Elliotthaseightnumberedcards.

Oneofthecardsischosenatrandom. Elliottsays: Theprobabilityofa8is� Therangeofthenumbersis5. Theprobabilityofanumbergreaterthan10is0. Theprobabilityofa7is� Fillinthesixmissingnumbers.

Question3: Thetwo-waytablegivesinformationabout90peoplewhosattheirdrivingtest.

(a)Completethetwo-waytable

Apersonispickedatrandom.

(b)Writedowntheprobabilitythatthepersonfailedtheirdrivingtest.

(c)Writedowntheprobabilitythatthepersonhadunder20drivinglessons.

Somebodywhopassedtheirdrivingtestispickedatrandom.

(d)Workouttheprobabilitythatthispersonhadunder20drivinglessons.

Question4: Isaachasmadetwofairspinners. Spinner1has10equalsizedsections. Spinner2has4equalsizedsections.

Isaacsays

“Itismorelikelytogeta4onspinner1thanspinner2becausetherearetwonumber4sonspinner1andonlyonenumber4onspinner2.”

ExplainwhyIsaacisincorrect.

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Question5: Thetableshowstheshoesizeof23students.

Astudentispickedatrandom.

(a)Workouttheprobabilitythatthestudenthasashoesizeof8. (b)Workouttheprobabilitythatthestudenthasashoesizeof7orsmaller.

Question6: Afootballteamcanwin,draworloseamatch. Thetableshowstheprobabilitiesofeachresult.

Eachwinisworth3points. Eachdrawisworth1point. Eachlossisworth0points. Thefootballteamplays40gamesinaseason.

Workouthowmanypointsthefootballteamshouldreceiveinoneseason.

Question7: Beatricehasabiasedfoursidedspinner. Thetableshowstheprobabilitiesthatthespinnerwilllandona2or3.

Theprobabilitythatthespinnerwilllandon1isthreetimestheprobabilitythat thespinnerwilllandon4.

Workouttheprobabilitythatthespinnerwilllandon1.

Question8: Finnhassomesweetsinabag. 5ofthesweetsarelemonYlavoured. 7ofthesweetsarestrawberryYlavoured. TherestofthesweetsaremintYlavoured.

TheprobabilitythatFinntakesamintYlavouredsweetis�

HowmanymintYlavouredsweetsareinthebag?

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Question9: Graciehasmorethan5coins. Thetotalvalueofthecoinsis50p.

Gracieisgoingtopickoneofthecoinsatrandom. TheprobabilitythatGraciepicksa1pcoinis�

ListallthecoinsthatGraciehas.

Question10: Aboxcontainslegoblocksofthesamesize. Eachblockiswhite,blue,greenorred.

Thetableshowstheprobabilitiesthatablockpickedatrandomiswhite,blueorred. (a)Workouttheprobabilityofagreenblock

Thereare60redlegoblocks.

(b)Howmanywhitelegoblocksarethere?

Question11: Abagcontainsgoodandbadapples. noftheapplesaregood. Theother5applesarebad.

(a)Writedownanexpression,intermsofn,forthenumberofapplesinthebagaltogether.

Maryamwilltakeatrandom,anapplefromthebag.

(b)Writedownanexpression,intermsofn,fortheprobabilitythatMaryamwilltakeagood apple.

(c)Writedownanexpression,intermsofn,fortheprobabilitythatMaryamwilltakeabad apple.

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Question12: Thereareonlyred,blackandgreenpensinabox.

Therearethreetimesasmanyredpensasgreenpens. Therearefourasmanyblackpensthanredpens.

Workouttheprobabilityofablackpenbeingselected.

� Answers

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