Statistics question based on Biggest Loser reality show.
There are 5 contestants with an equal chance of losing the highest and/or lowest percentage of body fat. The 4 contestants that lose the highest percentage make the final 4, and the contestant that loses the losest percentage is eliminated. Contestants are weighed in randomly. The weigh in begins. The first 4 contestants weigh in. The 3 contestants that have lost the highest percentage are determined, and are guaranteed a spot in the "final 4". The contestant, call her "A", that lost the lowest percentage of weight may still be eliminated. Now the 5th contestant, call her "5", is about to weigh in.
What are the odds that contestant "5" is eliminated because she has the lowest percentage of weight loss?

The odds are 1 in 5, or 20%.

There are five contestants. If the order of weigh-in is selected randomly, then there is a 1 in 5 chance that the last person to weigh in will be the one who has lost the least amount, regardless of what may happen with the preliminary weigh-ins by the first 4. Thus 20%.