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VJeyaa · Last edited by VJeyaa on Mon May 19, 2008 1:32 am; edited 2 times in total

A box with 2 coins

Imagine that you have two coins in a box and that one of the coins had heads on both sides, while the other had heads on one side and tails on the other. Question: if you remove one of these coins from the box and the visible side shows heads, what is the probabillity that the other side will also be heads?

This is an easy one. Wink

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Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.

tgopal · Junior Member Joined: 17 Mar 2008 Posts: 40

Kon_Roy · Posted: Fri May 09, 2008 1:12 pm Post subject:

VJeyaa · Posted: Thu May 15, 2008 3:41 pm Post subject:

any more guesses? Rolling Eyes

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Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.

blackmafia · Posted: Thu May 15, 2008 3:52 pm Post subject:

LoveSeeker · Junior Member Joined: 15 May 2008 Posts: 56

0.000000

rishi · Senior Member Joined: 06 Mar 2008 Posts: 620

0.5 or 0.25 Rolling Eyes

VJeyaa · Posted: Thu May 15, 2008 11:42 pm Post subject:

VJeyaa · Posted: Thu May 15, 2008 11:44 pm Post subject:

guys.... this is not a guessing game. A puzzle needs to be solved methodically to arrive at the answer. Probably you could guess for riddles, not puzzles....hahaha Wink

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Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.

VJeyaa · Posted: Fri May 16, 2008 11:29 am Post subject:

Okay, I will reveal the answer by noon.... if no further attempts are made by anyone.
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Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.

tgopal · Junior Member Joined: 17 Mar 2008 Posts: 40

VJeyaa · Posted: Fri May 16, 2008 12:05 pm Post subject:

Well not really. If that is the case, then it would be too simplistic to be a puzzle. I did say its easy, but NOT that simplistic. Wink

Your answer would be right if the coins are identical but the problem is they are not. One of the coins has heads on both sides. You need to factor that one in order to see the correct probability. See below illustration;

There are two sets of coin "states" in the box:

H / H
H / T

And you randomly choose one coin, so there are 4 choices.
( ) indicates the coin you choose:

(H) / H
H / (H)
(H) / T
H / (T)

Option 4 is not valid, because you can see a head. That reduces the valid states to 3, and the chance the other side is a head is therefore 2/3.
_________________
Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.