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An Amber-Colored Conundrum

The Puzzler


RAY: A few weeks ago, my younger son Andrew, who completed his first junior year in college, decided to come home for a few days to reacquaint himself with his parents.

TOM: Who, of course, are paying his tuition!

RAY: Right. He wanted to refresh his memory in case he had to identify us at the inquest.

He and I were driving around town, and he said, "Gee, I hadn't noticed that our town has changed a lot of its traffic signals to the new lights."

Now, traffic lights basically consist of a lens, like a green or a yellow, or a red lens, and a light bulb behind the lens. When the bulb goes on, you see the green, or the yellow, or the red light. The new traffic lights, however, are light-emitting diodes. Instead of having one bulb, you have perhaps dozens of diodes that are shining the light. The new lights are much cheaper to operate and they're much brighter.

TOM: And they don't all blow out at once!

RAY: Exactly. But, we noticed that there are some of the old lights still around. In fact, where they have put new ones in, they've replaced the green light and they've replaced the red light, but they haven't replaced the yellow lights.

I say, "It must be that they don't make light emitting diodes in yellow...maybe that's why they haven't replaced them."

We drove along a little farther, and Andrew says...

TOM: "Au contraire, piston puss!"

RAY: He says, "I think I have a better answer than that."

And, I said, "Yeah, it's about time." And he said, "As a matter of fact, it is about time." And that's the hint.

Why do we see new green lights and new red lights, but no new yellow lights?

Think you know? Drop Ray a note!

[ Car Talk Puzzler ]

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