Nice problem. I assume that in all three cases the initial grass volume on the pasture is the same. Let this volume bepunits (for "pasture"). Assume also that the grass growsgunits per day, and 100 sheep eatsunits of grass per day. The problem statement gives two equations in these three variables. Note however that the answer (the number of days corresponding to 1 hectosheep ) can be expressed as a function ofg/pands/p, and the two equations above can be rewritten as equations only ing/pands/p. Thus, we have two equations and two unknowns.