## 179. Math Puzzle $4 / 80$

On a bus line, ten vehicles operate at 15-minute intervals.

How many additional buses need to be deployed to ensure a 10-minute interval?
The shorter the headway between buses, the more vehicles will be required. Therefore, there is an inverse proportionality:

$$
\frac{15 \text{~min}}{10 \text{~min}}=\frac{x}{10}, \quad 10 x=150, \quad x=15
$$

Five additional buses will be required.