WOMAN: All right, Zach. Look what we have here. We've got two glasses. This is going to be your glass, and this is going to be my glass.

And here I've got some juice. I'm going to pour us some juice. And I'm going to pour us the very same amount of juice. OK.

All right, are those the same? What do you think? You want to measure them?

BOY: They're about the same.

WOMAN: Which one needs more? That one does? OK, I'll pour some more. what about now? Do we have the same?

BOY: Hm, just a little bit more.

WOMAN: A little bit more. What do you think?

BOY: They're the same.

WOMAN: OK. All right, so we have the very same amount of juice to drink? So if I drank my juice, and you drank your juice, we'd have the same?

BOY: If you drank more of what mine would be.

WOMAN: Oh. Well what if we both drank the whole thing. Would we drink the same amount of juice? OK.

Well watch what I'm going to do to my juice. Now, do we still have the same amount of juice, or does one of us have more?

BOY: The same.

WOMAN: They're the same? How can you tell that they're same?

BOY: Even though this one is lower, it's still the same amount of juice because it's wider and that one's taller.

WOMAN: Oh, OK. Well, I'm going to pour my juice back in this glass. Now do we still have the same amount of juice to drink? Yeah? How can you tell?

BOY: Because you poured that drink back in there and was the same before.

WOMAN: Oh, OK. Well, of course you're right again.