Question

How can you separate of iron filling and comman salt

Answer 1

By moving an magnet in mixture

Answer 2

The salt dissolves, the other solids do not. Using the fact that the iron is magnetic, the magnet can be used to separate the iron fillings from the mixture by moving teh magnet around in the container. Keeping the magnet in a plastic bag makes it easy to separate the filings from the magnet when you pull it out.