who needs a passing grade?

[radosr]

You failed a probability class, but you are given one last chance to pass. You are given 8 coins and told that 4 of them are magic. To you, the magic coins are indistinguishable from the others. You are allowed to partition all of the coins into two piles (not necessarily of the same size). If each pile contains exactly 2 magic coins, you get a passing grade. However, you are given only 3 tries to do it. Can you pass? If so, how?

 

[Aaron Wong]

I can't tell you because according to your problem I failed the probability class and therefore I cannot calculate my chances of passing.

 

[benzbubblecat]

are you allowed to remember which coins you moved and move those same coins, or are the piles effectively shuffled after each move?

 

[alain]

I can't tell you because according to your problem I failed the probability class and therefore I cannot calculate my chances of passing.

I like your answer but that was not the question.

 

[ferdowsi]

1) split into 2 piles of 4. If that fails, then you have either a 3-1 or 4-0 split of magic coins.
2) take 2 from pile 1 and switch with 2 from pile 2. If that fails, you originally had a 3-1 split and you either switched 2 magic for 2 non magic, or 1 of each for 1 of each.
3) combine the ones you switched. since they were either 2 magic and 2 non-magic or 2 sets of magic plus non-magic, this will guarantee 2 piles of 2 magic/2 non-magic.