There are three jelly beans on this stump; blue, red, and green. All three are delicious, BUT two of them are deadly poisonous, and will kill you within 30 seconds …. but one of them is safe to eat. You pick up the green one, and open your mouth …..
BUT WAIT! You are now told that the blue jelly bean is definitely poisonous, and it is removed from the stump. You still have the green one in your hand, and the red jelly bean sits on the stump.
You can eat the green one you are holding, or switch it for the red one. What do you do?
Scroll down for the answer!
When you first picked up the green jelly bean, there was a 1/3 chance that it was safe to eat, and a 2/3 chance that the safe one was still on the stump. But now that one of the two poisonous jelly beans has been removed from the stump, the one in your hand still has 1/3 odds of being safe, but you now know something about the red one waiting on the stump: if the safe jelly bean had been on the stump, the red one is safe.
Still confused? (don’t eat anything until you understand, haha!) It’s all explained here
Thanks to the fiendish minds at waitbutwhy for this very tough puzzle!