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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!

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Can You Guess the Secret Word in This Brain Teaser?
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On his YouTube channel Mind Your Decisions, Presh Talwalkar shares logic puzzles dealing with geometry, statistics, and algebra. The puzzle below from the former Stanford math and economics student features no numbers, but that doesn’t mean it's easy to figure out.

To solve the brain teaser, you need to guess the secret word based on a few clues. Here’s the set-up: A teacher is leading a class and Albert, Bernard, and Cheryl are his students. He writes the words "cat," "dog," "has," "max," "dim," and "tag" on the board. He distributes one sheet of paper to each of his three students, with each piece containing a different letter from one of the words. He then tells them that together their letters spell one of the words on the board. The students only know their letter, they don’t know anyone else's.

The teacher asks Albert if he knows the secret word. Albert says yes, he does know it. Next, the teacher asks Bernard. After some hesitation, he replies that yes, he knows the secret word as well. Finally, the teacher asks Cheryl if she knows what the word is. She thinks for a moment and says that yes she does. Albert, Bernard, and Cheryl have successfully guessed the secret word. Do you know what it is based on their answers?

Figuring out the word without knowing any of its letters may seem difficult, but it’s not impossible. If you don’t know where to start, think about Albert’s answer and use the process of elimination to rule out some of the letters and words written on the board. Keep in mind that Bernard could only come to his conclusion from Albert’s answer, and Cheryl from Bernard’s.

Still lost? If you haven’t gotten to the bottom of it yet, the correct answer is "dog." When Albert answers that he knows what the right word is based on one letter, you can use that information to narrow down his possible letters to one of the six that are never repeated on the board: c, o, h, s, x, and i. And when Bernard says that he knows too, you can deduce that his list of potential letters is limited to t, g, h, or s. That leaves "cat," "dog," and "has" as the three remaining options. Cheryl’s answer confirms that she has the letter d, which means the secret word is "dog."

If you’re looking for a more detailed walkthrough of the puzzle-solving process, check out the video from Presh Talwalkar below.

[h/t Mind Your Decisions]

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Can You Get to the Bottom of This Coffee Brainteaser?
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Is your brain awake and energized? If not, you may want to grab a cup of coffee to figure out this head-scratching puzzle.

According to IFL Science, the brainteaser was shared by Twitter user @_herbeautyxo and has been stumping web users ever since. The image shows coffee being poured into a network of pipes and boxes. It seems there are four places the liquid could end up and each is represented by a numbered cup. Based on the shape and arrangement of the pathways, you have to guess which vessel will catch the coffee first.

Plenty of users had guesses, but few of them answered correctly. But once you know what to look for, the puzzle becomes deceptively simple (scroll down if you want to find out the answer). 
 
 
 
 
 
 
 
 
 

Three of the four pipes are blocked off, so the only possible spot for the coffee to exit from is the remaining pipe above cup five.

Your brain doesn’t always interpret what you see in front of you accurately, even when it’s given a caffeine boost. If you need more evidence, check out these award-winning optical illusions and brain puzzles.

[h/t IFL Science]

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