An oil layer floats on 85cm of water in a tank. The pressure at the bottom of the tank is 113.0kPa .
How thick is the oil? Suppose that the density of oil is 900 kg/m3.
pressure p = 1atm + (ρgh)_water + (ρgh)_oil
113000 Pa = 101375Pa + 1000kg/m³9.8m/s²0.85m + 900kg/m³9.8m/s²h
3295 Pa = 8820Pa/m * h
h = 0.37 m = 37 cm
Hope this helps!