S&T 2nd round Brainteaser most people screw up!
Came across this MM S&T brainteaser and wanted to share it with you guys:
You have three pancakes. One pancake is burnt on one of it's two sides. Another is burnt on both of its sides. The last one is not burnt on either of its sides.
If we were to stack these three pancakes on top of each other and you can see that the top pancake is burnt on its top side, what is the probability that the top pancake is the pancake that is burnt on both sides?
Apparently, nearly everybody who interviews answers 1/2 but the correct answer is actually 2/3.
How anyone manages to get this brainteaser incorrect is beyond me :(
It's actually fairly simple to understand how someone could get this incorrect..
'2 of the pancakes have burnt sides and I see that the top one has a burnt side, therefore it is a 50% chance that the top one is burnt on both sides'
Your inability to consider someone else's thought processes is actually more dumbfounding to me.
Burn. Pun intended.
Pretty simple conditional probability, the trick is go by the number of sides not pancakes
P(Burnt both sides | Burnt) = P(Burnt both & Burnt) / P(burnt) = (2/6) / (3/6) = 2/3
Thanks!
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bayes rule, and it first looks non intuitive but actually makes sensee
bump, can someone explain this to me?
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