Hi I am solving some problems in fluid dynamics I came to this problem that I don't understand how to solve it. A piece of granite floats at the interface of mercury and water contained in a beaker (Fig.). If the densities of granite, water and mercury are ρ, ρ1 and ρ2 respectively, the ratio of the volume of granite in water to the volume in mercury is (a) (ρ2 – ρ) /(ρ – ρ1) (b) (ρ2 + ρ) /(ρ+ ρ1) (c) ρ1 ρ2 /ρ (d) ρ1 /ρ2 (e) ρ2 /ρ1 figure of problem is here --> http://www.apphysicsresources.com/2009/07/ap-physics-b-multiple-choice-questions.html I tried to approach it like this. we know that the granite will sink so we know that the pressure that water will put on the granite untill given height will be the same as buoyancy force of mercury,which is same as weight displaced. But I couldn't solve it in the end in terms of those variables I don't also understand the derivation in that link. Thanks in advance.