Would like to comment, but I never received either of the original problems!
> Date: Sun, 11 Aug 2013 16:00:13 -0400 > From: email@example.com > To: firstname.lastname@example.org > Subject: Re: Permutation problems > > The same fish/rat logic (inclusion/exclusion) needs to be applied to the second problem as well. For example, 9876450123 has been counted three times. > I believe the solution is: > 7!+8!+7! - (5!+4!+5!) + 2!