Money in Water
Braingle.com
on
Published in Brain Teasers
2/3
There are 3 possible combinations after you pull out 1 euro:
A 1 euro was in the river initially, and you pull out the second one you saw fall in; Therefore 1 euro is in the river still A 1 euro was in the river initially, but you pull it out; Therefore 1 euro is still in the river 2 euro fell in first, you pull out the 1 euro you saw fall in; Therefore 2 euro is still in the river. These three states are all equally likely, so there is a 2 in 3 chance of pulling out 1 euro
Today's brain teaser courtesy of Braingle.com.