1. The number of pairs of skew lines among all the edges of a regular pentagonal prism is $\qquad$ pairs.
This problem's difficulty: Easy for the first attempt
Mainly tests: Combinatorial counting
Solution: 50
There are $5 \times 4=20$ pairs between the two bases, and there are $10 \times 3=30$ pairs between the edges on the two bases and the vertical edges. Therefore, there are a total of 50 pairs.