On May 19, 1995, a blockbuster did something no action movie had ever done before:

It made viewers think about math.

The movie was Die Hard With a Vengeance. Where the first two Die Hards had trapped Bruce Willis’ John McClane inside single locations with a bunch of terrorists, With a Vengeance pitted him against master bad guy Simon Gruber (Jeremy Irons), who wants revenge for the time McClane threw his brother off a skyscraper. To get it, Simon sends McClane on a wild goose chase through Manhattan. Simon — who likes to preface his riddles and games with a sinister “Simon says!” — stages a series of impossible tasks McClane must accomplish in order to prevent a series of bombs from exploding around New York City.

The one Simon Says game everyone remembers from Die Hard With a Vengeance is also the simplest. For some reason, in a movie that involves wild car chases, Jeremy Irons’ German accent, and Bruce Willis dangling from the top of a moving subway car, this is the thing in it that everyone talks about. For 25 years, Die Hard fans have tried to solve ... the jug problem.

Here is how Simon puts it to McClane and his unwilling partner, a Harlem shopkeeper named Zeus (Samuel L. Jackson):

On the fountain, there should be two jugs: A five-gallon and a three-gallon. Fill one of the jugs with exactly four gallons of water and place it on the scale and the timer will stop. You must be precise; one ounce or more less will result in detonation.

Here’s the entire scene from the film:

I know less than nothing about math, but I’m going to assume this is a very old brain teaser. In the film, director John McTiernan doesn’t show the actual solution — he cuts away from McClane and Zeus and when he cuts back they’ve basically figured it all out.

In 1995, this drove me absolutely crazy: How could they make a math problem a major plot point and not explain how to solve it? I kept thinking about the jugs after I got home from the theater. I spent hours trying to solve it. (Again: I know less than nothing about math.) I couldn’t get it out of my mind.

Now I recognize McTiernan’s genius in that decision. By not showing the solution, he kept me thinking about that scene — and all that time thinking about the five-gallon jug and the three-gallon jug is precisely why I remember them now, 25 years later. It was like a cinematic mnemonic device.

Assuming you’re not sitting next to an explosive device that will explode in five minutes, and you’re not as bad at math as I was in eighth grade, it’s actually not a difficult problem. Here’s the solution:

  1. Fill the five-gallon jug.
  2. Fill the three-gallon jug with the water from the five-gallon jug, which now contains two gallons of water.
  3. Empty the three-gallon jug, then pour the two gallons from the five-gallon jug into it.
  4. Fill the five-gallon jug again.
  5. Pour the five-gallon jug into the three-gallon jug until it is filled. The three-gallon jug already had two gallons in it, so the one additional gallon leaves four gallons in the five-gallon jug.

Congratulations, you have beaten Simon’s problem! Unfortunately while you figured it out, he stole a giant pile of gold bricks. Happy 25th anniversary to Die Hard With a Vengeance, and to folks who love a little math with their explosions and chase scenes.

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