Question

Two quantities x and y are said to vary in inverse proportion, if there exists a relation of the type xy = k between them, k being a constant.

Answer 1

Given, two quantities x and y are said to vary in inverse proportion.
Then, $x\propto \frac{1}{y}$ or $y\propto \frac{1}{x}$.
In any case, we get $xy=\text{constant}$
Hence the given statement is true.