Question

The number of kilograms of water in a human body varies directly as the mass of the body. A 93-kg person contains 62-kg of water. How many kilograms of water are in a 75-kg person?

Answer 1

We know that the variation is proportianal, that is we can relate the quantities as:

$y=kx$

where y is the mass of the body and x is the mass of water. From the values given we have that:

$\begin{gathered} 93=62k \\ k=\frac{93}{62} \\ k=\frac{3}{2} \end{gathered}$

hence the constant of proportionality is 3/2. Now, if the mass of the water is 75, then the mass of the body is:

$\frac{3}{2}\cdot75=112.5$

Therefore, the mass of the body is 112.5 kilograms