# SG (Specific Gravity) in Fluid

## Homework Statement

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When asked for the bouancy of a hollow cylinder, containing air, submerged in ocean water.
Length of cylinder = L
The Material of the cylinder is neglected.

I'm thinking the Bouancy (Force) = ρ ⋅ g ⋅ v
where v = LπR^2 and therefore F = ρgLπR^2

But the solutions manual states it is
F = ρgLπR^2 ⋅ SG, where SG is Specific gravity of ocean water.
Why do I need the SG part ?