Last week I set readers the challenge which can be found here.
This one provoked quite a bit of debate, and not all of it Excel-related! As I already have to several readers, I must again apologize for the lack of realism and statistical know-how inherent in the premise for this challenge, which was evidently constructed more with the required formula-work in mind than with any serious thought to methods in demography.
Still, at least some fascinating and impressive Excel work came out of it all, so perhaps my poor groundwork is somewhat forgiven, at least retrospectively!