Probability Question : I have three locks and three keys (only One correct key for each lock).












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What is the probability that all locks are unlocked by choosing one key and one lock randomly at a time?
Note: After correctly choosing a key to unlock a lock, the key is kept back with the other two keys while the lock is kept aside. So after unlocking first lock, I am left with just 2 locks to choose from but I have all the three keys to choose from.



Please give some explanation to your answer as well.










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  • 2




    $begingroup$
    Can you at least answer this question: What is the probability that the first lock is unlocked?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 6:50






  • 1




    $begingroup$
    I am so sorry but I dont know as I am confused over this. I think It should be 1/3.
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:03






  • 1




    $begingroup$
    That’s right. Now when you get to the second lock, has anything really changed? You still have one chance in three of picking the right key, so the probability of unlocking the second lock is ... ?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:06










  • $begingroup$
    But in the first chance, I had three locks to choose from to apply my chosen key. In that scenario as well Would you say my answer was correct? Secondly, after successfully unlocking the first lock I ll hv to choose a lock from remaining 2 locks while I still choose a key from all the three keys.......
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:11










  • $begingroup$
    The choice of locks doesn’t make any difference. No matter which one you pick, you still have one chance in three of picking the right key.
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:21
















1












$begingroup$


What is the probability that all locks are unlocked by choosing one key and one lock randomly at a time?
Note: After correctly choosing a key to unlock a lock, the key is kept back with the other two keys while the lock is kept aside. So after unlocking first lock, I am left with just 2 locks to choose from but I have all the three keys to choose from.



Please give some explanation to your answer as well.










share|cite|improve this question









$endgroup$








  • 2




    $begingroup$
    Can you at least answer this question: What is the probability that the first lock is unlocked?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 6:50






  • 1




    $begingroup$
    I am so sorry but I dont know as I am confused over this. I think It should be 1/3.
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:03






  • 1




    $begingroup$
    That’s right. Now when you get to the second lock, has anything really changed? You still have one chance in three of picking the right key, so the probability of unlocking the second lock is ... ?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:06










  • $begingroup$
    But in the first chance, I had three locks to choose from to apply my chosen key. In that scenario as well Would you say my answer was correct? Secondly, after successfully unlocking the first lock I ll hv to choose a lock from remaining 2 locks while I still choose a key from all the three keys.......
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:11










  • $begingroup$
    The choice of locks doesn’t make any difference. No matter which one you pick, you still have one chance in three of picking the right key.
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:21














1












1








1





$begingroup$


What is the probability that all locks are unlocked by choosing one key and one lock randomly at a time?
Note: After correctly choosing a key to unlock a lock, the key is kept back with the other two keys while the lock is kept aside. So after unlocking first lock, I am left with just 2 locks to choose from but I have all the three keys to choose from.



Please give some explanation to your answer as well.










share|cite|improve this question









$endgroup$




What is the probability that all locks are unlocked by choosing one key and one lock randomly at a time?
Note: After correctly choosing a key to unlock a lock, the key is kept back with the other two keys while the lock is kept aside. So after unlocking first lock, I am left with just 2 locks to choose from but I have all the three keys to choose from.



Please give some explanation to your answer as well.







probability






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 8 '12 at 6:47









Jatin SehgalJatin Sehgal

61




61








  • 2




    $begingroup$
    Can you at least answer this question: What is the probability that the first lock is unlocked?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 6:50






  • 1




    $begingroup$
    I am so sorry but I dont know as I am confused over this. I think It should be 1/3.
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:03






  • 1




    $begingroup$
    That’s right. Now when you get to the second lock, has anything really changed? You still have one chance in three of picking the right key, so the probability of unlocking the second lock is ... ?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:06










  • $begingroup$
    But in the first chance, I had three locks to choose from to apply my chosen key. In that scenario as well Would you say my answer was correct? Secondly, after successfully unlocking the first lock I ll hv to choose a lock from remaining 2 locks while I still choose a key from all the three keys.......
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:11










  • $begingroup$
    The choice of locks doesn’t make any difference. No matter which one you pick, you still have one chance in three of picking the right key.
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:21














  • 2




    $begingroup$
    Can you at least answer this question: What is the probability that the first lock is unlocked?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 6:50






  • 1




    $begingroup$
    I am so sorry but I dont know as I am confused over this. I think It should be 1/3.
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:03






  • 1




    $begingroup$
    That’s right. Now when you get to the second lock, has anything really changed? You still have one chance in three of picking the right key, so the probability of unlocking the second lock is ... ?
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:06










  • $begingroup$
    But in the first chance, I had three locks to choose from to apply my chosen key. In that scenario as well Would you say my answer was correct? Secondly, after successfully unlocking the first lock I ll hv to choose a lock from remaining 2 locks while I still choose a key from all the three keys.......
    $endgroup$
    – Jatin Sehgal
    Nov 8 '12 at 7:11










  • $begingroup$
    The choice of locks doesn’t make any difference. No matter which one you pick, you still have one chance in three of picking the right key.
    $endgroup$
    – Brian M. Scott
    Nov 8 '12 at 7:21








2




2




$begingroup$
Can you at least answer this question: What is the probability that the first lock is unlocked?
$endgroup$
– Brian M. Scott
Nov 8 '12 at 6:50




$begingroup$
Can you at least answer this question: What is the probability that the first lock is unlocked?
$endgroup$
– Brian M. Scott
Nov 8 '12 at 6:50




1




1




$begingroup$
I am so sorry but I dont know as I am confused over this. I think It should be 1/3.
$endgroup$
– Jatin Sehgal
Nov 8 '12 at 7:03




$begingroup$
I am so sorry but I dont know as I am confused over this. I think It should be 1/3.
$endgroup$
– Jatin Sehgal
Nov 8 '12 at 7:03




1




1




$begingroup$
That’s right. Now when you get to the second lock, has anything really changed? You still have one chance in three of picking the right key, so the probability of unlocking the second lock is ... ?
$endgroup$
– Brian M. Scott
Nov 8 '12 at 7:06




$begingroup$
That’s right. Now when you get to the second lock, has anything really changed? You still have one chance in three of picking the right key, so the probability of unlocking the second lock is ... ?
$endgroup$
– Brian M. Scott
Nov 8 '12 at 7:06












$begingroup$
But in the first chance, I had three locks to choose from to apply my chosen key. In that scenario as well Would you say my answer was correct? Secondly, after successfully unlocking the first lock I ll hv to choose a lock from remaining 2 locks while I still choose a key from all the three keys.......
$endgroup$
– Jatin Sehgal
Nov 8 '12 at 7:11




$begingroup$
But in the first chance, I had three locks to choose from to apply my chosen key. In that scenario as well Would you say my answer was correct? Secondly, after successfully unlocking the first lock I ll hv to choose a lock from remaining 2 locks while I still choose a key from all the three keys.......
$endgroup$
– Jatin Sehgal
Nov 8 '12 at 7:11












$begingroup$
The choice of locks doesn’t make any difference. No matter which one you pick, you still have one chance in three of picking the right key.
$endgroup$
– Brian M. Scott
Nov 8 '12 at 7:21




$begingroup$
The choice of locks doesn’t make any difference. No matter which one you pick, you still have one chance in three of picking the right key.
$endgroup$
– Brian M. Scott
Nov 8 '12 at 7:21










1 Answer
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$begingroup$

Possible combinations are 3×2×1=3!=6
In which 1 is correct
P(A)=1÷6=0.166






share|cite|improve this answer









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    1 Answer
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    1 Answer
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    0












    $begingroup$

    Possible combinations are 3×2×1=3!=6
    In which 1 is correct
    P(A)=1÷6=0.166






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      Possible combinations are 3×2×1=3!=6
      In which 1 is correct
      P(A)=1÷6=0.166






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        Possible combinations are 3×2×1=3!=6
        In which 1 is correct
        P(A)=1÷6=0.166






        share|cite|improve this answer









        $endgroup$



        Possible combinations are 3×2×1=3!=6
        In which 1 is correct
        P(A)=1÷6=0.166







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 15 '17 at 6:58









        Pankaj JorwalPankaj Jorwal

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