Can You Solve the Airplane Fuel Riddle?

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Getty Images

Here's a fun riddle: Professor Fukanō plans to circumnavigate the world in his new airplane. But the plane's fuel tank doesn't hold enough for the trip—in fact, it holds only enough for half the trip. But with the help of two identical support planes (which can refuel him in mid-air) piloted by his assistants Fugori and Orokana, the professor thinks he can make it in one trip. But since all three planes have the same problem of limited fuel, how can they work together to achieve the professor's goal without anyone running out of fuel?

This TED-Ed riddle is very much like a Popular Mechanics riddle written in 2016. It's a tricky one, and it helps to have a piece of paper handy.

It's explained in the video below (along with a "pause now" bit so you can solve it yourself). If you're not a fan of video, here are the starting rules:

1. The professor's plane must make a single continuous trip around the world without landing or turning around.

2. Each plane can travel exactly 1 degree of longitude in 1 minute for every kiloliter of fuel. Each can hold a maximum of 180 kiloliters of fuel.

3. Any plane can refuel any of the others in mid-air by meeting at the same point and instantly transferring any amount of fuel.

4. Fugori and Orokana's planes can turn around instantaneously without burning fuel.

5. Only one airport is available for any of the planes to land, take off, or refuel.

6. All three planes must survive the experiment, and none may run of fuel in mid-air.

As the video explains, the airport mentioned in point #5 happens to be on the equator.

Here's the video:

For a bit more from TED-Ed on this riddle, check out this lesson page. If you want to read a solution to a very similar puzzle without watching the video above, try this Math is Fun puzzle page.

Wednesday’s Best Amazon Deals Include Computer Monitors, Plant-Based Protein Powder, and Blu-ray Sets

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Amazon
As a recurring feature, our team combs the web and shares some amazing Amazon deals we’ve turned up. Here’s what caught our eye today, December 2. Mental Floss has affiliate relationships with certain retailers, including Amazon, and may receive a small percentage of any sale. But we only get commission on items you buy and don’t return, so we’re only happy if you’re happy. Good luck deal hunting!

Never Got a Snoopy Sno-Cone Machine as a Kid? You Can Still Buy One This Holiday Season

LUCKYPENNY VIA YOUTUBE
LUCKYPENNY VIA YOUTUBE

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Even as toys have gotten more complex in recent decades, one low-tech item has held a perennial spot on holiday wishlists. The Snoopy Sno-Cone Machine was a hit when it debuted in 1979, and kids and nostalgic adults can still get their hands on one this December.

People who grew up in the 1980s may remember commercials promoting the “yum-yum fun” plastic appliance. Like the Easy Bake Oven and the Frosty Sno-Man Sno-Cone Machine before it, the Snoopy Sno-Cone Machine allowed kids to make edible treats at home. The Peanuts branding made the toy popular with kids, and despite the elbow grease required to crank a couple of ice cubes into shaved ice, it's stuck around.

If you asked for a Snoopy Sno-Cone Machine for the holidays as a kid and never received one, you can still make your childhood dreams come true. The retro product is available practically unchanged from how it appeared in the 1980s. The biggest changes are that the hand crank is now easier to turn and there's a clamp for stabilizing the machine while you use it. Get one for yourself or a loved one from Amazon today for $30.

Looking for more nostalgic gift ideas? Here are some items the Millennials in your life will love.