The most unexpected answer to a counting problem with solution

The most unexpected answer to a counting problem with solution 

Obviously, Numberphile also described this problem (I hadn’t seen it): https://youtu.be/abv4Fz7oNr0
However, I believe this video is wrong. There is a factor of 16 in everything that shouldn’t be there, unless they make an additional assumption that I’m not aware of. Also, the solutions I’m going to share are a bit more detailed and geometric than the ones shown here.

Stay tuned for the full explanation

Great video 

Watch and learn

Solution : So why do colliding blocks compute pi?