RAY: Hi, we're back. You're listening to Car Talk with us, Click and Clack, the Tappet Brothers. And here's the answer to last week's puzzler. Some of you may recall that --

TOM: I remember the puzzler.

RAY: My brother embarrassed us some weeks ago by stating that Martin Gardner was dead. And his son Jim called us to tell us that his father insists he isn't.

TOM: He called and said, "I'm not dead. Tell them I'm not dead."

RAY: Anyway, he offered us, Martin himself, offered us a puzzler for use in our show and actually Jim stated the puzzler last week and here it is.

TOM: And did a pretty fine job of it, I thought.

RAY: He did.

TOM: Yeah.

RAY: Better than we do.

TOM: Yeah.

RAY: Maybe he's, maybe he wants to come out of retirement. There are three on-off light switches on the wall of the first floor of a building. One switch, one of the switches, one of the three controls a bulb in a lamp on the third floor of the building. The other two switches, like my brother and I, are disconnected. They're not connected to anything.

TOM: They, they do nothing.

RAY: Yeah. You're allowed to toggle the switches as many times as you want. Then you're allowed to walk just once, so you can do it, you can turn switches on one, you can turn all three of them on, you can turn all three of them off, you can turn two on, three on, one on, you can do whatever you want for as long as you want. Okay? Then you're allowed to walk just once to the third floor to check the light bulb.

TOM: Right. And then you have to decide, which one of the switches on the first floor is in fact the one that turns the light bulb on or off. This is a great puzzler. Martin Gardiner is good. Especially considering that he's dead.

RAY: Well here's the answer.

TOM: Yeah.

RAY: You turn the first switch on. You leave it on for ten minutes. Why, you ask? You'll see in a minute. Then you turn it off and you turn the second switch on and you go upstairs.

TOM: And you leave the third switch in the off position.

RAY: There you go.

TOM: Yeah.

RAY: If the bulb is on, then it's switch number two, which is the one that's on.

TOM: Right.

RAY: OK? If the bulb is off and it's cold, then it's switch number three, which is the one you never touched, that controls that light. If the bulb is off but it's hot, then it was switch number one.

TOM: Excellent.

RAY: Pretty cool, huh?

TOM: This is an excellent, this qualifies as an excellent puzzler. Cause it seems so impossible. This is a Martin Gardiner puzzler.

RAY: It's right up there.

TOM: It's right up there.

RAY: It's right up there with one of his. Who's our winner this week?

TOM: Chip Merrow from Loudon, New Hampshire. Loudon, is that how you pronounce it?

RAY: Loudon.

TOM: Loudon, New Hamster.

RAY: It's not hamster.

[ Car Talk Puzzler ]