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# Can you solve this fiendishly difficult brainteaser involving jelly beans?

If you think you'll get this riddle correct, think again.

Tim Urban and Andrew Finn over at waitbutwhy have created a fiendishly difficult brain-teaser, and it goes something like this:

### There are three jelly beans coloured green, red and blue and two of them are deadly poisonous.

Picture: waitbutwhy

It continues:

Two of the jelly beans on the stump are poisonousâ€”youâ€™ll die within 30 seconds of eating either one of them. But one of the jelly beans isnâ€™t poisonous and wonâ€™t harm you at all. All three of the jelly beans are delicious. The situation works like this: You pick one of the jelly beans and eat it, and if you happen to pick the non-poisonous one, youâ€™re free to go.

### Except *wrong.*

The green bean is actually twice as likely to kill you than the red one.

Why?

Tim Urban explains:

When you initially picked the green jelly bean, there was a 1/3 chance that it was the safe one to eat, and a 2/3 chance that it was poisonous and the safe one was still on the stump. When the man removed a poisonous blue jelly bean from the stump, it told you no new info about the green jelly bean in your hand â€” that still had a 1/3 chance of being safe. But removing the blue jelly bean told you a lot about the red jelly bean â€” it told you that if the safe jelly bean had been on the stump, the red one is safe.

Based on the Monty Hall Game Show Problem involving two goats and a car behind three separate doors, Marilyn Savant put it a different way:

If you pick door one, and then you are told door three has a goat behind it, do you then switch to door two?

Yes you should switch. The first door has a 1/3 chance of winning, but the second door has a 2/3 chance.

Hereâ€™s a good way to visualize what happened. Suppose there are a million doors, and you pick door number one. Then the host, who knows whatâ€™s behind the doors and will always avoid the one with the prize, opens them all except door number 777,777. Youâ€™d switch to that door pretty fast, wouldnâ€™t you?

Source: thegiflibrary