Question 1206988
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Zack, Susie and Peter all face to the left in the order presented.


Zack can only see the wall.
Susie can only see Zack's hat.
Peter can see Susie's hat and Zack's hat.


All three participants know the number of hats and number of each color. 
It is assumed that each participant also follows a logical process without randomly guessing. Also, each participant will change their thought process based on what the others call out (or lack of call out). 


There are 4 possible scenarios
(a) Zack and Susie both are wearing a red hat
(b) Zack and Susie both are wearing a black hat
(c) Zack wears a red hat, Susie wears a black hat
(d) Zack wears a black hat, Susie wears a red hat


If scenario (a) was the case, then there aren't any red hats left, and Peter would call out "black".
However, Peter remains silent. 
Peter's silence allows both Zack and Susie to rule out scenario (a).


If scenario (c) was the case, then Susie would call out "black". But like Peter she is silent as well.
Her silence lets Zack rule out scenario (c).


In cases (b) and (d), Zack is wearing a black hat. 
Unfortunately there isn't enough info to determine the hat color for Susie or Peter.



Answer: Black
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