[ Numerical inequalities. Comparing numbers.]

It is known that the values of the expressions $b / a$ and $b / c$ are in the interval $(-0.9, -0.8)$. In which interval do the values of the expression $c / a$ lie?
Let's rephrase the problem: $x \in\left(\frac{8}{10},\frac{9}{10}\right), y \in\left(\frac{10}{9},\frac{10}{8}\right)$; in which interval does $x y$ lie?

The answer is obvious: in the interval $\left(\frac{8}{10} \cdot \frac{10}{9},\frac{9}{10} \cdot \frac{10}{8}\right)=\left(\frac{8}{9},\frac{9}{8}\right)$.

## Answer

In the interval $\left(\frac{8}{9},\frac{9}{8}\right)$.