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? Think carefully first, then make a decision:
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. So the answer is 20.