Problem of the Week, #119

A colleague Bill Wardlaw (March 3, 1936-January 2, 2013) used to create a “Problem of the Week” for his students, giving a prize of a cookie if they could solve it. Here is one of them.


A spider puts on 8 identical socks and 8 identical shoes (and of course the spider has 8 feet). In how many different ways can the spider do this, given that on each foot, the sock has to go on before the shoe?