a boat floats in water with 2/5th of in=ts volume outside water. If the density of water is 1000 kgm the density of the boat of material is ?

Let,  volume of boat = V

        density of boat = ρ

        mass of boat = M

        Density of water = ρ_w = 1000 kg/m³

Volume of the boat  immersed in water = V' = V – 2V/5 = 3V/5

mass M = density x volume = ρ.V

According to Archemedes Principle,

Buoyant force = volume displaced x density of fluid x g

                    = V' x ρ_w x g

Weight of the body is balanced by the buoyant force.

Weight of the displaced water = Buoyant force

 mg = V' x ρ_w x g

(ρ.V)g = 3V/5 x ρ_w x g

ρ = 3/5 x ρ_w

   = 3/5 x 1000

   = 600 kg/m³

As the density of boat is less than that of water, boat is floating on water.