Final answer:
Fernando maintains a 25 to 6 ratio of country to rock songs. His road trip playlist with 25 country songs, therefore, has 6 rock songs.
Step-by-step explanation:
Fernando wants to maintain the same ratio of country songs to rock songs in all of his playlists. In the summer playlist, the ratio of country songs to rock songs is 100 to 24. This ratio can be simplified by dividing both numbers by their greatest common divisor, which is 4. The simplified ratio is 25 country songs to 6 rock songs.
Since Fernando's road trip playlist has 25 country songs, and we have established that the ratio of country songs to rock songs is 25 to 6, we can directly infer that there are 6 rock songs on his road trip playlist to maintain the same ratio.