Brain Teasers
Brain Teasers Trivia Mentalrobics Games Community
Personal Links
Submit a Teaser
Your Favorites
Your Watchlist
Browse Teasers
All

Cryptography
Group
Language
Letter-Equations
Logic
Logic-Grid
Math
Mystery
Optical-Illusions
Other
Probability
Rebus
Riddle
Science
Series
Situation
Trick
Trivia

Random
Daily Teasers
Search Teasers

Advanced Search
Add to Google Add to del.icio.us

More ways to get Braingle...

Money in Water

Probability puzzles require you to weigh all the possibilities and pick the most likely outcome.

 

Puzzle ID:#3265
Fun:*** (2.44)
Difficulty:*** (2.19)
Category:Probability
Submitted By:cathalmccabe***
Corrected By:cowman12

 

 

 



You drop two coins into a muddy river by mistake. You saw one falling in, a 1 Euro coin. You know the other one had to be either a 1 Euro coin, or a 2 Euro coin.

After searching and pulling out one, and discovering it's a 1 Euro coin, what is the chance that the other is also a 1 Euro coin?



Answer

2/3

There are 3 possible combinations after you pull out a 1 Euro:

A 1 Euro was in the river initially, and you pull out the second one you saw fall in; therefore a 1 Euro is in the river still.
A 1 Euro was in the river initially, but you pull it out; therefore a 1 Euro is still in the river.
A 2 Euro fell in first, you pull out the 1 Euro you saw fall in; therefore a 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 a 1 Euro.

Hide




What Next?

  
  

See another brain teaser just like this one...

Or, just get a random brain teaser

If you become a registered user you can vote on this brain teaser, keep track of
which ones you have seen, and even make your own.

 






Back to Top
   



Users in Chat : dodger 

Online Now: 7 users and 323 guests

Copyright © 1999-2014 | Updates | FAQ | RSS | Widgets | Links | Green | Subscribe | Contact | Privacy | Conditions | Advertise

Custom Search





Sign In A Create a free account