Arithmetic

A lady comes into the Dominion one evening. She selects four rental tags from the rack and then selects a movie from the sales rack, bringing them all up to the counter. Fernando sets about filling out the rental slip and gathering the films in question while the woman digs out a $10 bill from her purse and sets it on the counter.

“The total comes to $15,” Fernando explains when all five discs are gathered and he begins transferring the purchased film—The Last Airbender—to the DVD case proper. The woman replaces the $10 and exchanges it for a $20, and the transaction goes through and she leaves.

About two minutes later she comes back waving the receipt.

“The sign says it's rent one get one free,” the woman says.

“That...is correct,” Fernando says. “Hence why the total came to $15.”

“Well, I bought a movie. That should make one of the DVDs free.”

Fernando raises his eyebrows. “Ok, we'll go with that. $8 for the purchase, plus two $3.50 rentals makes $15.”

“But I get one free because I bought one. You just said so.”

“I'm not disagreeing. But that still makes $15 total.”

“I don't understand. I bought the movie and that gets me one free. Then I rented another one and get another one free.”

“Yep,” Fernando agrees. He points to the fifth rental. “But that one is unattached. Hence not free. Hence $3.50 rental. Hence $7 for two rentals, plus $8 for the purchase, makes $15. If you would like to return one of them, I could certainly refund your money.”

Confusion flickers across the woman's features. “I don't want a refund. I want to get one free.”

“You're getting two free,” Fernando patiently explains. He plucks five slips of paper from his fill-me-out-weekly-drawing bucket and divides them into three groups. “Purchase plus free rental,” he says, pointing to one group. “Rental and free rental,” he continues, pointing to the second. “Additional, not-free rental,” he concludes, pointing to the lone fifth paper slip. “Now, if you like, you could pick up a sixth movie. That one would certainly be free, because you have this fifth one here by itself. But the fifth one is not by itself free.”

A pregnant silence lingers between Fernando and the lady, while Law and Order: SVU drones on about rape in the background.

Finally, she speaks. “I still don't get it.”

And people wonder how on earth the data could support the US scoring so poorly in mathematics compared to other countries in the world.