4 aliens and 4 chairs

Probability Level pending

Four aliens sit in four chairs, but they don't always sit in the chairs correctly... Sometimes they face forward, and sometimes they face backward.

How many different ways can the four aliens sit in the four chairs?

Clarification : The chairs are in a row and are distinct. The aliens are also distinct (as are their fronts and backs). Each alien can choose a different chair and a different way to face. So for example, the first chair could have a blue alien facing backward or a red alien facing forward.


Image credit: http://drydenart.weebly.com/


The answer is 384.

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1 solution

Geoff Pilling
Feb 6, 2017

First off there are 4 ! = 24 4! = 24 ways they can choose the order of how they sit.

Once they have sat down, each has 2 2 ways to sit, so they can sit 2 4 = 16 2^4 = 16 different ways.

24 16 = 384 24 \cdot 16 = \boxed{384}

Can you mention that the chairs arranged linearly and not in a circle.

Siva Bathula - 4 years, 4 months ago

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Good point... I've edited the problem.

Geoff Pilling - 4 years, 4 months ago

pssst! I think you mean 4 ! = 24 4! = 24 ways. 24 ! 24! is approximately Avogadro's number!

Brian Moehring - 4 years, 4 months ago

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Haha... Yup, good catch, I've updated it! ;-)

Geoff Pilling - 4 years, 4 months ago

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