The Necklace

A necklace weighs 50 g in air, but it weighs 46 g in water. Assume that copper is mixed with gold to prepare the necklace. Find how much copper is present in it. (Specific gravity of gold is 20 and that of copper is 10 .)

A jeweller claims that he sells ornaments made of pure gold that has the relative density of 19.3. He sells a necklace weighing 25.250 g f to a person. The clever customer weighs the necklace when immersed in pure water and finds that it weighs 23.075 g f in water. Is the ornament made of pure gold?