Suppose there are three cards: a black card that is black on both sides,
a white card that is white on both sides, and a mixed card that is black on one side and white on the other.
All the cards are placed into a hat and one is pulled at random
and placed on a table.
The side facing up is black.

What are the odds that the other side is also black?

This is like the old vinyl records (45 rpm) where there have never been two good sides:

if we know side One:

Bad: bad -> bad

Mixed: bad -> good

if we know side Two:

Bad: bad -> bad

Mixed: good -> bad

As 'bad' is already given, we will have 'bad' again in 2 out of 3.

Steve Herman is right.

Edited on June 8, 2017, 4:35 pm

Posted by ollie on 2017-06-08 16:34:38