1. The problem statement, all variables and given/known data If the population y of rats on a farm at time t (in weeks) satisfies: dy/dt = -y(y-100)/50 then how many rats per week should be killed to eradicate the population? 2. Relevant equations None known. 3. The attempt at a solution The ODE dy/dt is autonomous, so I can use a phase line. I found the equilibrium points to be at y=0 and y=100, and found that for the interval 0<y<100, solutions were increasing, and for both the intervals 100<y<%infinity, and -%infinity<y<0, solutions were decreasing, but the third interval is probably undefined, since a negative population is not feasible. And now I'm lost. I don't know what to do after I've worked this out! Thanks in advance for your hints.