Imagine a question and stream-of-consciousness explanation for which this is the answer: 20
Question: In a show, there can be 5 actors at a time. Every actor is in the show for about 15 minutes, and then another 5 actors come in. How many actors can there be on the show in 1 hour?
Stream-of-consciousness: One hour is 60 minutes, so there can be 60 / 15 = 4 different sets of actors. This means, that during one hour there can be 4 * 5 = 20 different actors in the show.