On a wire, 9 swallows are sitting at regular intervals from each other. The distance between the first and the last swallow is $720 \mathrm{~cm}$.

- What is the distance between neighboring swallows?
- How many swallows would be sitting on the wire if three more swallows sat between each pair of the already sitting swallows?

(M. Krejčová)
Among nine swallows, there are only 8 gaps.

1. The distance between neighboring swallows is $720: 8=90(\mathrm{~cm})$.
2. If 3 new swallows perched in each of the eight gaps, a total of $8 \cdot 3=24$ swallows would perch. There would then be $9+24=33$ swallows on the wire.

Evaluation. 1 point for the observation about the number of gaps; 2 points for the first part; 3 points for the second part of the problem.