Low Tide

Feb 08, 1997

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...

RAY: ...because the porthole's distance from the water doesn't change at all. If the boat is floating, it will continue to float and the porthole will be raised up as the boat is raised up and the distance will be the same.

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