1. The problem statement, all variables and given/known data Water in a tank is uniformly bubbled with small identical air bubbles each having volume V0. A sphere of mass M and volume V floats in water due to the attachment of certain number of air bubbles in the surface.If dw is the density of water,and the minimum number of air bubbles that is needed to be attached to keep the sphere floating in water is n, then (1) n =( M-Vdw)/ (V0dw ) (2) n > ( M-Vdw)/ (V0dw ) (3) n < ( M-Vdw)/ (V0dw) (4) n > ( V0dw )/( M-Vdw) (5) n < ( V0dw )/( M-Vdw) 2. Relevant equations 3. The attempt at a solution For the sphere to float,the density of water+ air bubble mixture should be more than the density of the sphere (I think?). Assuming it is so, dw + n/v0 > M/V n/v0 > M/V - dw I get n > [ (M - dw*V)/V ] * V0 which is not among the choices given so I hope someone can tell me where I'm going wrong. Thank you.