Thanks for the explanation, but I cannot follow on this line
Since he knows that Bernard doesn’t know given just the row, each ball in that row is in a column that contains more than one ball.
Why is that? Why couldn’t it be A2 or A3? In this case neither Albert nor Bertrand could tell what row/column this was either, because it would be in a row/column with another ball. How can you exclude any row with overlap with any single-ball columns?
It couldn’t be row A or B because there would then be a possibility the ball was in A6 or B5 and that Bernard actually did know where the ball was. Albert says he knows Bernard doesn’t know where the ball is, which means he is 100% confident, and the only rows that allow for that confidence are rows C and D, because each ball in each row is not alone in its column.
Scenario 1: The madman tells you the ball is in row A. Then the madman whispers the column to Bernard. Can you really be sure that Bernard knows or doesn’t know where the ball is?
Scenario 2: The madman tells you the ball is in row C. From this, you can be completely sure that Bernard doesn’t know where the ball is, because any column he would be given doesn’t narrow it to a single row.
Thanks for the explanation, but I cannot follow on this line
Why is that? Why couldn’t it be A2 or A3? In this case neither Albert nor Bertrand could tell what row/column this was either, because it would be in a row/column with another ball. How can you exclude any row with overlap with any single-ball columns?
It couldn’t be row A or B because there would then be a possibility the ball was in A6 or B5 and that Bernard actually did know where the ball was. Albert says he knows Bernard doesn’t know where the ball is, which means he is 100% confident, and the only rows that allow for that confidence are rows C and D, because each ball in each row is not alone in its column.
Scenario 1: The madman tells you the ball is in row A. Then the madman whispers the column to Bernard. Can you really be sure that Bernard knows or doesn’t know where the ball is?
Scenario 2: The madman tells you the ball is in row C. From this, you can be completely sure that Bernard doesn’t know where the ball is, because any column he would be given doesn’t narrow it to a single row.
Oh of course, I didn’t consider the “I know you don’t either” part. Thanks, I got it now :)