Consider two identical containers. Container A is filled with water to the top. Container B has a block of wood floating in it, but the level of the water is also at the top. Which container weighs more

Container A will weigh more

Explanation:

Both containers are identical, so we assume that they weigh the same.

They both have the same volume, and will contain an equal volume of a material.

Since they both contain water to the top, this means that their volume is fully occupied. But container B contain a block of wood floating in it.

The fact that the block of wood floats in the water in container B shows that it is less dense than the water around it, and in the container A, this same space is completely filled with water.

What we derive from this is that the portion of space contained by the block of wood in container B is occupied by water in container A, but, in container B, the density of this space is lesser now, since the wood block floats.

Since density is mass per unit volume, and weight is proportional to mass, then we can see that the weight of this volume portion in container B is lesser than that of container A. The consequence is that container A will weigh more than container B because of this extra weight.