Hard
Genius Level Riddles
15 XP

The Sleeping Beauty

16,885 solved 81% solve rate 19% fail rate
Sleeping Beauty is put to sleep. A coin is flipped. If heads, she wakes Monday only. If tails, she wakes Monday and Tuesday (memory wiped between). Upon waking, what probability should she assign to heads?
Only 81% solve this correctly
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Quick Answer & Explanation
This is debated: thirders

The answer to this riddle is This is debated: thirders. Difficulty: Hard · Solved by 16,885 puzzle lovers.

This is debated: thirders say 1/3, halfers say 1/2. Both have rigorous philosophical arguments.
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