The traditional method of measuring a person's bodyfat ratio is to weigh them on dry land and then weigh them while submerged in water. The bodyfat ratio can be calculated using the difference in these weight measurements. Unfortunately, this method requires that the person become submerged in water, which is a problem for those suffering from hydrophobia (fear of water).

Angel investors give money to companies that they think have highly marketable products or services in exchange for partial ownership of the company. A company has mailed a proposal to investors seeking money to market a new device for measuring a person's bodyfat ratio with no need for the person to get wet.

In the company's proposal, the person in the figure is standing on a weight scale in a sealed chamber. Initially, the chamber is maintained at standard atmospheric pressure. However, the pressure is then lowered and the new weight is noted.

Derive an expression for the density of the person in terms of his weight before (1)

and after (2) the chamber is evacuated. Use 1 and 2

for the density of the air before and after the chamber is evacuated.

p=