How to find out the truth? Archimedes thought about the problem day and night. One day he was about to have his bath, but he was busy thinking. He did not notice the bathtub. The water in the bathtub was already full to the brim. He slid into the bathtub. Immediately a large quantity of water flowed over the brim of the bath tub. He noticed this suddenly. His brain wave worked suddenly. He jumped out of the bathtub, shouting, “Eureka! Eureka!" Eureka in Greek means “I have found it."

Different metals of the same weight have different volumes. Objects, put in water, will displace water. The displaced water will be equal to their volume.