RAY: This is a puzzler for the kids. There is a yacht tied to the dock in the harbor at dead low tide. The tide, because it is dead low, is obviously doing what ...

TOM: Coming in.

RAY: And it is coming in at the rate of two-thirds of a foot per hour. A steady rate of two-thirds of a foot per hour. Right. So, if you were in the harbor and you were measuring the rate, after a half hour it would have come in a third of a foot.

TOM: Got it.

RAY: The porthole on the side of the yacht is 9 feet above the surface of the water. How many minutes will it be until that distance is reduced from 9 feet to 7 and a half feet. I made it hard, I could have said 7 and a third feet, but I didn't want to. And I will give a hint - you can't use algebra to solve this problem...