As Shown in the Figure, a Large Open Tank Contains $m ^ { 3 }$

Short Answer

As shown in the figure, a large open tank contains a layer of oil ( density 450 kg/ $m ^ { 3 }$ ) floating on top of a layer of water (density 1000 kg/m³) that is 3.0 m thick, as shown in the sketch. What must be the thickness of the oil layer if the gauge pressure at the bottom of the tank is to be $8.5 \times 10^4 \mathrm {~Pa} ?$