Answer
The percentage of the body weight that is composed of fat is 19.8%
Work Step by Step
We can find the mass of the fat:
$m = \rho~V = (890~kg/m^3)(0.020~m^3) = 17.8~kg$
We can find the fraction of the body mass that is composed of fat:
$\frac{17.8~kg}{90.0~kg} = 0.198$
The fraction of the body weight that is composed of fat is equal to the fraction of the body mass that is composed of fat. Therefore, the percentage of the body weight that is composed of fat is 19.8%.
