MathDB
CNCM Online R1P1

Source:

September 2, 2020

Problem Statement

Pooki Sooki has 88 hoodies, and he may wear any of them throughout a 7 day week. He changes his hoodie exactly 22 times during the week, and will only do so at one of the 66 midnights. Once he changes out of a hoodie, he never wears it for the rest of the week. The number of ways he can wear his hoodies throughout the week can be expressed as 8!2k\frac{8!}{2^k}. Find kk.
Proposed by Minseok Eli Park (wolfpack)