Harry Potter platform, why 9 and 3/4? [symbol of number]

#HarryPotter went to the platform 9 and 3/4 to go to the magic world.
why did the author choose 9 and 3/4 as the number of #platform?
this video explains the reason by math, especially number symbolism.
#symbol of 9 goes well with that platform. let's go to math travel.

introduction to 9 and 3/4
the author’s mention about 9 and 3/4.
the symbol of 9
the examples using the symbol of 9

Видео Harry Potter platform, why 9 and 3/4? [symbol of number] канала Math Travel