The outer core is less dense than which of Earth's layers?

The mantle is composed of dense, rocky material which ranges from being virtually solid near the lower boundary with the core, to more squidgy towards the boundary with the overlying layer, the crust. Mantle material is less dense than the core, but still denser than the outer layers of the earth.

The solid, inner most layer of the Earth, composed of iron and nickel under extremely high pressure and temperature. The inner core is more dense is the answer.