What is the weight of the water displaced by the block of wood?
According to Archimedes’ Principle, “any body fully or partially submerged in a fluid is buoyed up by a force equal to the weight of the fluid displaced”. The weight of the water displaced is the same as the total weight of the wood block. The fact that 1/3 of the block is above the water level does not matter if you just weigh the total block of wood – then the weight of the total block of wood = the weight of the water displaced by the block of wood. If you want to find density of the block of wood that is a different question – then you need the volume of the block of wood and the information about “one- third of the total weight” .
