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Ask iit jee aieee pet cbse icse state board community Community Discussion Question: probablity
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jic (5)

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1) In a jar there are 3 white marbles and 7 black marbles.You draw a marble and see

if it is black .If so , you stop.Otherwise,you keep the marble and draw again.You

repeat this process untill u draw a black marble.


a) Find the probablity that 3 draws are needed.


c) Find the probablity that 5 draws are needed.

    
aditi_g (355)

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is the answer to the first part 7/120??
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aditi_g (355)

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hey wat do u mean by keep the marble?? u mean bak in the jar or keep it out??
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aditi_g (355)

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if it means we keep thm out thn answer wud be 7/120 for first part and 0 for second
if it means tht we keep it bak in the jar thn ans to the first one is 63/1000
and second part wud be 567/100000
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rishipratimm (492)

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in case u r talkin bout drawin aftr replacin d marbles
prob of drawin a white marble = 3/10
in case 3 draws r neede,
we get net prob = 3/10 * 3/10 * 7/10

i case 5 draws r neede,
we get net prob = (3/10)^4 * 7/10

"Many of the things you can count,dont count....
Many of the things you cant count,really do count...."-Albert Einstein

"The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them"-William Bragg

"An inexplicable fact is infinitely preferable to an incomprehensible mystery"-F. Soddy


RISHIPRATIM MAZUMDAR
NIT DURGAPUR
1ST YEAR,ELECTRONICS AND COMMUNICATIONS
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rishipratimm (492)

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@aditi
i guess it shud b considerin relacemnt,
cos i dnt thnk they will ask a q where d ans to a probability will come out to b zero..
bt datsmy guess agn...

"Many of the things you can count,dont count....
Many of the things you cant count,really do count...."-Albert Einstein

"The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them"-William Bragg

"An inexplicable fact is infinitely preferable to an incomprehensible mystery"-F. Soddy


RISHIPRATIM MAZUMDAR
NIT DURGAPUR
1ST YEAR,ELECTRONICS AND COMMUNICATIONS
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aditi_g (355)

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yep havent seen any ques wid zero as ans... thn it wud be wid replacement but its not very clear so i gave both
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rishipratimm (492)

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good thinking!!!
lol!

"Many of the things you can count,dont count....
Many of the things you cant count,really do count...."-Albert Einstein

"The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them"-William Bragg

"An inexplicable fact is infinitely preferable to an incomprehensible mystery"-F. Soddy


RISHIPRATIM MAZUMDAR
NIT DURGAPUR
1ST YEAR,ELECTRONICS AND COMMUNICATIONS
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aditi_g (355)

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thanx lol..
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