I think there is some ambiguity in the question.

>>> (All this time you don't know you were tossing a fair coin or not).
1) Does the above statement mean that the thower don't know whether he
or she threw a fair coin even after throwing? Or is the thrower not
informed beforehand that one of them is not a fair coin?
2) Does the coin count reduce after every throw or should it be put
back?
3) Depending on 1) and 2), there will be different answers.


On Aug 9, 12:13 am, Maddy <madhu.mitha...@gmail.com> wrote:
> I think the answer is 17/80, because
> as you say the 5 trials are independent.. but
> the fact that a head turns up in all the 5 trials, give some
> information about our original probability of choosing the coins.
>
> in case we had obtained a tail in the first trial, we can be sure its
> the fair coin, and so the consecutive trials would become
> independent..
>
> but since that is not the case, every head is going to increase the
> chance of choosing the biased coin(initially), and hence affect the
> probability of the next head..
>
> before the first trial probability of landing a head is 3/5, but once
> u see the first head, the probability of landing a head on the second
> trial changes to 4/5*1/4+1/5, and so on..that is, there is a higher
> probability that we chose a biased coin, rather than the fair coin.
>
> hope its clear..
>
> On Aug 7, 11:36 pm, sumit gaur <sumitgau...@gmail.com> wrote:
>
>
>
> > (3/5)
>
> > On Aug 7, 10:34 pm, Algo Lover <algolear...@gmail.com> wrote:
>
> > > A bag contains 5 coins. Four of them are fair and one has heads on
> > > both sides. You randomly pulled one coin from the bag and tossed it 5
> > > times, heads turned up all five times. What is the probability that
> > > you toss next time, heads turns up. (All this time you don't know you
> > > were tossing a fair coin or not).- Hide quoted text -
>
> - Show quoted text -

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