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. Do you remember last week's puzzler?

TOM: Not, not at all.

RAY: Not really. I didn't think so.

TOM: I honestly don't have the vaguest idea --

RAY: And it was you, I believe, who said "good puzzler"

TOM: Did I?

RAY: I think so.

TOM: Well, that's good.

RAY: Here it is.

TOM: Go ahead. It'll come to me, of course.

RAY: Oh, it's gonna. As soon as I say the first three words, you're going to say - I remember it! A mother has two kids and the older one is a boy.

TOM: I still don't remember it.

RAY: The chances that the younger --

TOM: Oh, that one. Yeah. I get it now.

RAY: The chances that the younger kid is a boy are 50-50. Right?

TOM: Yeah.

RAY: That's pretty simple.

TOM: Sure.

RAY: Almost anyone could have gotten that just by what? Guess work.

TOM: Well, most people think that the chances of everything is 50-50.

RAY: Is 50-50 especially when there are boys and girls involved.

TOM: Yeah.

RAY: Now, here's the puzzler. Suppose a mother has two kids and not the older one, but just one of them is a boy, what are the chances that the other one is also a boy?

TOM: Phew.

RAY: Now if you draw little pictures. There are four possible scenarios.

TOM: Yeah.

RAY: Older boy, younger boy. We'll call that B and B. Older boy, younger girl. Older girl, younger boy.

TOM: Um hmm. Yeah.

RAY: And older girl, younger girl. That's it. If you're going to have two kids, that's it. All right? Now, in the first case --

TOM: Of course.

RAY: If I say... When I say the older one is a boy --

TOM: Um hmm.

RAY: That it immediately leaves out the last two --

TOM: Exactly.

RAY: Possibilities.

TOM: That's right.

RAY: OK? It can only be boy-boy or boy-girl.

TOM: That's right.

RAY: Right. So, in order for it for the other one to be a boy, it's a 50-50 chance.

TOM: Right. You can have boy-boy, boy-girl.

RAY: Right. Or, now... Now!

TOM: Yeah.

RAY: When I say that one of them is a boy, I believe... Believe it or not it is this counterintuitive --

TOM: It certainly is.

RAY: It becomes harder for the other one to become a boy.

TOM: Um hmm.

RAY: And the chances are one in three cause if you look at the scenarios, you have boy-boy, boy-girl and girl-boy.

TOM: Sure.

RAY: Right? For the other one to be a boy, it's gotta be choice #1 which is boy-boy cause you already said that one of them is a boy, how can the other one be a boy? There's one chance in three. Hard to believe. Isn't it?

TOM: It's hard to believe.

RAY: I don't believe it.

TOM: I don't either.

RAY: Well, it's --

TOM: But it is true.

RAY: It is true.

TOM: And evidently, evidently Marilyn has a lot of data and the way she... I remember this puzzler now. You said you stole it from Marilyn.

RAY: Well, I didn't really steal it from Marilyn, I stole it from Steven Miller.

TOM: Yeah, but don't forget, Marilyn stole it from somebody else so, it's fair game. But the way that she proved it, she said here's how I'm going to prove it and she asked people to send her letters --

RAY: Oh yeah.

TOM: Anyone who had two kids and the first one was a boy, how many had a second one a boy and two kids who, one of whom was a boy, how many had second one as a boy --

RAY: Right, and --

TOM: And it came out --

RAY: She proved it empirically --

TOM: Empirically.

RAY: Just like we did with the Monty Hall thing.

TOM: Exactly, which I guess is OK, but I like the more elegant, abstract mathematical solutions, myself. I mean, but that's the kind of guy I am, I'm an abstract kind of guy.

RAY: You're abstract all right. Do we have a winner this week?

TOM: I don't remember. Uh. Ha! Yes, we do. The winner is David Ward from Atlanta, Georgia.

[ Car Talk Puzzler ]