# Math forum

 a simple question of probability Options
mohit
 #1 Posted : Sunday, April 17, 2011 8:23:44 AM

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###### A box contains two coins. One coin is heads on both sides and the other is heads on one side and tails on the other. One coin is selected from the box at random and the face of one side is observed. If the face is heads what is the probability that the other side is heads?
 #2 Posted : Monday, April 18, 2011 9:09:39 AM
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Ans: 2/3

sample space for d open side is a head: {hh, hh, ht}

so now, no. of events wen d othr side is also a head= 2

no. of elements in sample space= 3

so, probability= 2/3

mohit
 #3 Posted : Friday, April 22, 2011 8:32:03 AM

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madhuri , ur solution is incorrect...both the heads are identical so there cant be 2 HH in the sample space...well this qstion has to b solved by using conditional probability which is covered in class 12 of cbse...if u r younger than i dont think u will be able to solve it by using conditional probability... btw ur answer is absolutely correct.. :)

 #4 Posted : Monday, April 25, 2011 2:53:30 PM
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okay.. i thought i was ryt.. btw, m in 12th nw n i dint do probability yet!! so i was unable to find d solution in a ryt way. :(

newayz my ans was ryt.. :) :)

mohit
 #5 Posted : Tuesday, April 26, 2011 7:21:36 PM

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yeah...u will learn conditional probability later nd then u will b able to solve it.. :)

 #6 Posted : Wednesday, April 27, 2011 4:45:22 PM
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yeah, but plz tel me d ans now..

ayaanin
 #7 Posted : Wednesday, September 28, 2011 3:20:36 PM
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Gyanesh Kumar Verma
 #8 Posted : Thursday, May 10, 2012 7:37:30 AM
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[quote=ayaanin]

agreeing with ayaanin.....

because it's clearly mentioned from question that if the coinn taken out shows heads so there are two options left.... head or tell which implies probability as 1/2.....

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