divdude, you've got the answer!! According to ur chart, if all the rats die, it can be concluded that bottle 1 conatains poison; if rats 1 and 3 die, bottle 3 contains poison; if only rat 1 dies, bottle 7 contains poison, and so on. The basic idea here is that with n rats we can have a unique combination of rat(s) tasting water from each of 2^n bottles. So, the combination of rats that die will indicate which bottle contains poisonous water. freek, i don't see how both of them are 1. divdude, wt. of potatoes remaining = 50 lb.