--- Lee Corbin <lcorbin@ricochet.net> wrote:
> Here is a problem that I left off my original post
> because I thought that it was too similar to one of
> the four. But maybe not. Possibly, it may clarify
> the current discussion.
>
> 5. There are two cards in a hat: one is red on one
> side
> and blue on the other side. The other is red on
> both
> sides. You reach into a hat and select one of
> the
> cards at random, and slap it down on the table.
> If a
> red surface is now showing, what is the
> probability
> that the other side is red?
2/3
If you don't specify the color showing, it's 3/4, 4
possible sides, 3 of which have a red side opposite.
OTOH, your chance of getting the card with a blue side
is 50/50... the 2/3 results because you exclude 1/2
the times the card with the blue side is picked in
your initial conditions.
Loree
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