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Double black (Posted on 2017-06-08) Difficulty: 3 of 5
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?

No Solution Yet Submitted by Ady TZIDON    
Rating: 2.6667 (3 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
45 rpm | Comment 3 of 4 |

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

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