Question

A large ice cube floats in a glass of water.

There is a steel bolt frozen inside the ice cube. What happens to the water level when all the ice melts? (No water is lost due to evaporation.)
The water level will rise.
Without knowing the mass of the bolt, we cannot answer this question.
The water level will fall.
The water level will not change.

Answer 1

suppose $\rho$ _steel is density of a bolt

according to the equilibrium

( M + m ) g = V $\rho$ _w g

( M + m ) = V $\rho$ _w

V = ( M / $\rho$ _w ) + ( m / $\rho$ _w )

if ice is going to melt to water then the volume is

V ' = ( M / $\rho$ _w ) + ( m / $\rho$ _steel )

V ' < V as the density $\rho$ _steel > $\rho$ _w  

so The water level will fall.

third option is correct