Question

If 20% of an object is submerged in water, what is its density?

Answer 1

a floating body displaces its own mass of the fluid in which it floats.....

Answer 2

The weight of the displaced water = weight of the object

Answer 3

But
Weight w=mg

Answer 4

Here g is a constant

Answer 5

So mass of displaced water= mass of the object

Answer 6

hint:
if I call with V_0 the volume of your object, then the volume of the part submerged is 0.2*V_0. Now we have to apply the Priciple of Archimewde, so we get:

\[\Large {\delta _O} \times {V_0} \times g = {\delta _W} \times 0.2 \times {V_0} \times g\]
where g is gravity, g=9.81 m/sec, and
\[\Large {\delta _O},\;{\delta _W}\]
are the densities of the object and the water respectively