# The Problem

• Four men are buried up to their necks in the ground, as illustrated.
• They cannot move, so they can only look forward.
• Between A and B is a brick wall which prevents either side from seeing the other.

# The Question

• Which one calls out the color of their hat?
• Why is he 100% certain of the color of his hat?

# Data

• We have 4 cowboys (yeehaw!), each wearing 1 hat, either white or black.
• They are buried in 4 spots, unable to move, or rotate their heads, constraining their field of view forward.
• The wall prevents A from seeing B, C, D, and vice-versa.

# Information

• A and B can only see the wall. They cannot turn their heads to look behind them.
• Immobile and buried in a straight line, C sees B, and D sees C and B; no one sees A.
• No one knows their own hat color.
• Each cowboy knows the others’ position.

# Knowledge

• The 4 companions get 1 shot to get this right, if not, they all get shot.
• None of them will call out early, unless they are 100% certain of their hat color, because they all value their lives. Granted, they might do a 9th minute “Hail Mary” [see cultural football reference] guess, but luckily, one of their companions yelled out the right answer in under a minute. So, we know he wasn’t “guessing”.
• We also know that A and B don’t matter, because they are equally ignorant of one another, as well as everyone else, due to their positions.
• Looking at the options, comprehensively, we see that only a select few of them fit with our observations.
• 4 slots [1,2,3,4]
• 2 options each {B, W}
• only 2 of each (2Bs, 2Ws)

# Insight

• We know that D has the most data, but surprisingly, he doesn’t call out for a good minute, despite being able to see both B and C.
• C notices that D doesn’t call out, despite D having more direct observable data.
• C quickly reasons that D doesn’t know, despite his vantage point. (A key point, C will now exploit!)
• So, we can now intuit that C has more (indirect) information than D as we pass the 1-minute mark, given D’s response (or lack of).
• C can exploit the fact that, among the 2 remaining scenarios D is contemplating, both scenarios constrain C’s hat color (Black).

# Action

## More from Abhikhya Ashi

Developer and Designer

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## Abhikhya Ashi

Developer and Designer