One For One

An off-and-on gentleman enters the store one day. Fernando uses the phrase “off-and-on” because this guy has rather frequent run-ins with the law and spends a fair amount of time under the hospitality of the local criminal justice system. Despite his illicit proclivities, he has never failed to return his movies on time when he comes in to rent, so Fernando does not shy away from renting to the gentleman. He's a Keeper of the Dominion, not the Morality Police of the External World.

Anyhow, it's a Tuesday and Tuesday, in addition to being New Release Tuesday, is Rent One Get One Free. The man browses the store for a bit and then approaches the counter with a small handful of tags. “It's one for one today, right?” he asks.

“It's rent-one-get-one, yeah,” answers Fernando.

“Not one for one?” the man asks in confusion.

Fernando notices the man's befuddlement. “I mean, it's always one for one. If you pay to rent a movie you are entitled to the borrowing of that movie. But today you get a free rental when you rent a movie. 'Two for one' would be a more accurate way to phrase it.”

“Wait, when did you start this?” he asks.

“Um. It's been that way since time immemorial. Anyway, it comes to seven bucks.”

“Wait. You said it's two for one.”

“Right.”

“I have three movies.”

“Right.”

“So I should only have to pay for one of them.”

“I don't follow.”

“It's two for one, not one for one,” the man explains.

“Right. That's why it's seven dollars.”

“But you said it's two for one.”

Fernando eventually makes it clear to the man how the values “two” and “one” are not interchangeable in any regard.