Puzzle #52: Vampires

Vampires are very in. It has not always been this way though. Not so long ago, we greeted the bloodsuckers with crosses and wooden stakes. They had to be much more careful and ensure that they were not noticed.

Suppose they had to leave all but one in 200 people alone to avoid detection. Of those who were eligible to be midnight snacks, 90% of them could contribute once per year; 7% twice per year; 2% four times per year; and that last 1%, we do not know how many times yet.

Assume that a vampire has to feed twice per month, the vampire population stays constant, the carrying capacity of Kamloops is 28 vampires, and Kamloops has 90,000 breathers. The final 1% must be able to be snacked on at least how many times per year for the above conditions to work out? (The results of population figure percentage calculations should not be rounded.)

Submit your answer to Gene Wirchenko <genew@telus.net>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, June 4, 2014 at noon Pacific Time. I will post the answer shortly after.