Why and how did the density of water change when salt was added to it?

I think the main reason that this happened is because that when salt is dissolved in the water, since salt have mass, it will increase the mass of water. As density equals to mass divided by volume, more mass divided by the same amount of volume will give a result of more density of water. The density of water is now higher and when the egg is put into the water, the water's density is higher than the egg's thus, the egg floated.

Aloysius Chan