1. The problem statement, all variables and given/known data At what depth a lake surface is the total pressure 3 times the normal atmospheric pressure? 2. Relevant equations P=pgh this is the equation for liquid pressure. About total pressure we should add also the atmospheric pressure which is pushing from above the surface of the liquid. 3. The attempt at a solution Pl + Patm=pgh so, 300kPa=1000kg/m3*10m/s2*h... the answer is 30m, but in the answer key is 20m.