Probability of misprints on each page

[Dhamnekar Win,odd]

My answer to (a)

 

N= Total symbols on each page. r= 50 misprints. So, what is impossible is two or more misprints occurring in the same symbol. So, first condition of Fermi-Dirac statistics is satisfied. All distinguishable arrangements satisfying the first condition have equal probabilities. In our case, It is [math]\binom{500N}{50}^{-1}[/math]

 

Edited August 13, 2022 by Dhamnekar Win,odd