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Tue 23 Sep, 2003 12:08 pm
This was an interesting problem submitted to Marilyn for her weekly column in Parade Magazine.
Say you are sitting in a dark room where you are handed a deck of 52 cards. Ten of those cards have been turned facing up; the rest are facing down.
Your job is to separate the cards into two stacks, each containing the same number of cards facing up.
HINT: They do not have to be equal stacks -- just that each stack must contain the same number of cards facing up.
Can you do it -- and explain why it works?
Frank I dont know if this is what you mean, but here is one way it could be done.
http://www.ahs.uwaterloo.ca/~museum/vexhibit/plcards/vision/vision.html
Nope.
Actually, if you deal out ten cards from the deck -- and turn them over -- you will have as many up cards in the ten card pile as you have in the remaining 42 card pile.
It has to work if you think about it.
But that only works if you know that the 10 cards facing up are not included in the ten you flipped... although...
*thinks about it*
if they were in the ten you flip over, then they would be facing down and would cancel each other out...
okay so yeah it does work... !!!
jinnee wrote:But that only works if you know that the 10 cards facing up are not included in the ten you flipped... although...
*thinks about it*
if they were in the ten you flip over, then they would be facing down and would cancel each other out...
okay so yeah it does work... !!!
One doesn't often see someone change his/her mind in the middle of a post like that...but it was fun to see it happen here! :wink:
And fun to read, too. (I like Marilyn's column.)
The thing I like about this puzzle is that it shows the limits we
unconsciously put on ourselves. Nothing in the problem said you could
not turn cards over, yet we assume that it would be "against the rules."
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