This is basically just the "how many piano tuners are there in NYC" question rephrased. The point is that someone talks through their thought process. The solu

This is basically just the "how many piano tuners are there in NYC" question rephrased. The point is that someone talks through their thought process. The solution is to say, "Well, you need to know the volume of a ping pong ball, the volume of the trailer, and the packing density of spheres. Ping pong balls are a few centimeters across, 3 maybe?, so their volume is about..."