Questions & Answers about El viaje duró tres días.
Why use duró instead of tardó, since this lesson is about tardar?
Why is duró in the preterite tense here instead of the imperfect (duraba)?
The preterite (duró) is used because the trip is viewed as a completed event in the past. Stating a specific, closed timeframe like tres días triggers the preterite because you are looking at the total completed time of the action from beginning to end.