IIT JEE , AIEEE Forum - Mathematics , Algebra - very imp-probability!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! help!!!!!!!!!!!!

sweetgal17

there are 3 similar coins one of which is ideal and the other two aare biased.........the chances of getting head are 1/2 1/3 and 2/3.....a coin is selected at random and tossed twice. if head occurs both times find the probablty thtttt ideal coin was selected !!!!!!!!!!!!!!

sprinkle

Let
A - event that head occurs twice when a coin is tossed twice
B - event that ideal coin was selected
C - event that biased coin was selected (for which prob of H is 1/3)
D - event that biased coin was selected (for which prob of H is 2/3)

Now,
The probability that ideal coin was selected given that head occurred both times

= P(B/A)

= P(B

A) / P(A)

= P(B) P(A/B) / (P(A

B) + P(A

C) + P(A

D)

= P(B) P(A/B) / (P(B)P(A/B) + P(C)P(A/C) + P(D)P(A/D))

= (1/3)(1/2 * 1/2) / ((1/3)(1/2 * 1/2) + (1/3) (1/3 * 1/3) + (1/3)(2/3 * 2/3))

= 9/29 ANS

sweetgal17

u r too good dude.... cheers.... i wanna rate u...how should i???
tell me??

aakash.dixit

sweetgal ji can you not see this below post

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sprinkle sir tussi great ho ji

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