HardMath and Logic
1/1000 trick coin. Flip 10 heads. Prob it's the trick coin?
Riddle
1/1000 trick coin. Flip 10 heads. Prob it's the trick coin?
Choose an answer
A.1/1000
B.1/1024
C.99/100
D.~1/2
Hint: It's a word with 0 letters, starting with "~".
Answer
~1/2
Why this is the answer
Bayes' Theorem: Prior prob of trick coin is 0.001. Prob of 10 heads given trick is 1. Given fair is (1/2)^10 = 1/1024. These are almost equal, so probability is about 0.5.
This riddle is filed under Expert Riddles for Adults and rated Hard.
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