YouTube // TED-Ed
YouTube // TED-Ed

Can You Solve 'Einstein's Riddle?'

YouTube // TED-Ed
YouTube // TED-Ed

In this TED-ED video, we're presented with what's called "Einstein's Riddle." As the video-makers admit, it apparently has nothing to do with Einstein, aside from being a fairly tough puzzle to crack. If you enjoy logic puzzles, you'll want to set aside ten minutes for this one!

"Einstein's Riddle" is a form of Zebra Puzzle, in which you're provided with a series of facts, then asked to deduce one fact that's not presented. In the video's case, it's the location of a fish that has been kidnapped. There are five identical houses in a row (numbered one through five), and one of them contains the fish. Can you figure out which house it is, with only the clues provided?

If you're not in a place to check out the video, here are the starting assumptions:

1. Each house's owner is of a different nationality (German, Norwegian, Danish, British, Swedish); drinks a different beverage (tea, milk, coffee, root beer, water); and smokes a different brand of cigar (Pall Mall, Prince, Blends, Dunhill, Blue Master).

2. Each house's interior walls are painted a different color (blue, green, yellow, red, white.)

3. Each house contains a different animal (horse, dog, cat, bird, fish). You're looking for that fish!

And here are all the clues:

1. The Brit lives in the house with red walls.

2. The Swede has a dog.

3. The Dane drinks tea.

4. The house with green walls is directly to the left of the house with white walls.

5. The owner of the house with green walls drinks coffee.

6. The person who smokes Pall Mall cigars owns a bird.

7. The owner of the house with yellow walls smokes Dunhill cigars.

8. The man living in the center house drinks milk.

9. The Norwegian lives in the first house.

10. The man who smokes Blends lives next to the cat owner.

11. The horse's owner lives next to the man who smokes Dunhill.

12. The man who smokes Blue Master drinks root beer.

13. The German smokes Prince.

14. The Norwegian lives next to the house with blue walls.

15. The man who smokes Blends has a next-door neighbor who drinks water.

Can you figure out which of the five houses has the fish?

For more on this puzzle, check out this TED-Ed lesson page. It also links to a bunch of similar puzzles, in case this is your jam!

This Might be the World's Hardest Jigsaw Puzzle

For advanced jigsaw puzzle players, the standard 1000-piece board is child's play. But imagine if none of those pieces had a cute cat or weeping willow on the front to guide you.

The “Black Hell” puzzle—or “White Hell,” depending on your color preference—by Japanese manufacturer Beverly features a single solid color on its front. Adding an extra layer of frustration, the company claims its micro-sized puzzle pieces are the “world’s smallest,” suitable only for the nimblest of fingers.

One reviewer said it took him 17 months to complete half the puzzle. Another commented, “This puzzle is the devil reincarnated into an inanimate object!”

Although the front of the puzzle is blank, different patterns are imprinted on its back to help users connect the dots. This apparently disappointed one especially masochistic puzzle enthusiast, who wrote that it was “less impossible than I had hoped.”

The recommended age for this puzzle is seven years and up, but it’s safe to say that this devilishly hard task is best left to professionals.

While the Black Hell is certainly in the running for the most challenging jigsaw puzzle, it doesn’t top the chart for ones with the most pieces. Amazon sells a few 9000-piece puzzles, and ones with 5000 pieces are easy to find.

The Math Puzzle That’s Driving the Internet Bananas

Here at Mental Floss, we love a good brain teaser—and clearly we’re not alone. From cows and chickens to river crossings, we’ve never met a riddle we didn’t want to solve—even if it was originally meant for a 5-year-old. The Bananas, Clock, Hexagon Viral Logic Puzzle, which math puzzle enthusiast Presh Talwalkar posted to his Mind Your Decisions blog, is the latest riddle to have us admittedly stumped.

According to Talwalkar, 99 percent of the people who attempt to solve the problem fail, leaving the remaining one percent to be dubbed geniuses for figuring it out. Which side will you land on?

The key to solving this puzzle is to look closely. We’ll give you a minute to do just that (or you can start the video below—it will give you a little time before giving anything away).

Now it’s time to come up with your answer. We’ll give you another minute …


So what did you come up with?

If you answered 38, congratulations—you might be a genius.

If you answered something else, don’t worry, you’re not alone.

Where most people seem to be going wrong with the problem is by not looking at the images closely enough when attempting to assign a numerical value. Specifically: In the last line of the problem, all of the images—the clock, the bananas, and the hexagon—are all slightly different than the images shown in the previous lines. If you noticed this, then you probably realized that the bunch of bananas in lines one, two, and three have a different value than the fruit seen on line four. Same goes for the clock and the hexagons. Which makes this as much a visual puzzle as it a math problem.

Finish watching the video above for Talwalkar’s detailed explanation of how to solve the problem. Then stump your friends!

[h/t: Mind Your Decisions]


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