TED-Ed
TED-Ed: Daniel Finkel: Can you solve the unstoppable blob riddle?
A shooting star crashes onto Earth and a hideous blob emerges. It creeps and leaps, it glides and slides. It's also unstoppable: no matter what you throw at it, it just re-grows and continues its rampage. The only way to save the planet...
TED-Ed
TED-Ed: Can you solve the giant spider riddle? | Dan Finkel
Once every century, the world's greatest spiders gather to compete in a series of grueling games. The winner will become the next arachnomonarch, able to command all the world's spiders to their will. That day is today, and for the first...
TED-Ed
TED-Ed: Can you solve the Alice in Wonderland riddle? | Alex Gendler
After many adventures in Wonderland, Alice has once again found herself in the court of the temperamental Queen of Hearts. She's about to pass through the garden undetected, when she overhears the king and queen arguing that 64 is the...
TED-Ed
TED-ED: Can you solve the buried treasure riddle? - Daniel Griller
After a massive storm tears through the Hex Archipelago, you find five grizzled survivors in the water. As an act of gratitude for saving them, they reveal a secret _ the island they were just on holds some buried treasure. But when the...
Curated Video
TED-Ed's Frog Riddle Is Wrong
TED-Ed presented a riddle last week based on a classic probability problem. However in the riddle there is a small and seemingly insignificant detail that changes the calculation. In this video I present the pertinent details of the frog...
Curated Video
The 3 Jug Riddle
You have a full 12 liter jug and empty 5 and 8 liter jugs. Can you measure exactly 6 liters? This problem dates to 1484 and was posed in the context of a milkman making a home delivery to a customer. The story goes this riddle so...
Curated Video
Elon Musk's Favorite "Impossible" Riddle - One Mile South, One Mile West, One Mile North
I'm somewhere on earth. I walk one mile south, one mile west, and one mile north. I end up exactly where I started. Where am I? This puzzle is a classic brain teaser that was asked at Microsoft. It is also one of the favorites of Elon...
Curated Video
The Seemingly IMPOSSIBLE Cyclist And Motorcycles Riddle
Thanks to Alessio from Italy for creating this problem and sending it to me! A cyclist and a series of motorcycles are racing to the top of a long climb, and the cyclist doubles back. Given how many motorcycles passed the cyclist, can...
Curated Video
VERY HARD South Korean Geometry Problem (CSAT Exam)
Thanks to Hyeong-jun (H. J.) for emailing me this problem! This is a challenging problem from the math section of the 1997 CSAT, a standardized test in South Korea. Can you figure it out? It took me several attempts, but it was really...
Curated Video
Can You Solve The Hardest Easy Geometry Problem?
In the figure, what is the value of angle x? This problem is known as Langley's Adventitious Angles. It is also known as the hardest easy geometry problem because it can be solved by elementary methods but it is notoriously difficult to...
Curated Video
A 16 Year Old Discovered This AMAZING Geometry Hidden Pattern. Pascal's Theorem
Pascal discovered this amazing geometry result when he was only 16. The book "The Art of the Infinite" by Robert Kaplan and Ellen Kaplan has a wonderful introduction to projective geometry and a proof this this theorem. Proof of Pascal's...
Curated Video
Can You Solve It? Avoiding The Troll Probability Riddle
Every day you walk from A to B. But your journey is unpredictable: randomly on half of the days, a troll blocks your path and forces you to walk around an invisible barrier. What is your best strategy to walk the least distance on...
Curated Video
Can You Solve This MIT Admissions Question? Geometry Problem, 1869
The Massachusetts Institute of Technology (MIT) is one of the top ranked universities in the world. This question appeared on its admissions exam nearly 150 years ago. "The perpendicular dropped from the vertex of the right angle upon...
Curated Video
Evil Geometry Problem
A geometry textbook has the following problem: "A right triangle has a hypotenuse equal to 10 and an altitude to the hypotenuse equal to 6. What is the area of the triangle?" Can you figure out the correct answer? Blog post (text/image...
Curated Video
MIND-BLOWING MATH DISCOVERY - Multiply Numbers By Lines Rotation Geometry
Since 2007, millions of people have watched videos on "how the Japanese multiply," also known as "Chinese stick multiplication" or "Vedic Math." With millions of people watching these videos, you would expect everything is known about...
Curated Video
HOW SMART ARE YOU? The Stolen Bill Riddle (Viral Math Problem) - The Correct Answer Explained
This problem is making the rounds on Facebook and Twitter with thousands of people arguing about the correct answer. How smart are you? A guy walks into a store and steals a $100 bill from the register without the owner's knowledge. He...
Curated Video
Can You Solve The Chess Competition Riddle?
Thanks to Mika from Sweden for suggesting this problem! Most of the games end in a draw, but some will be wins for you, and others will be wins for your skilled opponent (details in video). The first player to win 2 games in a row is...
Curated Video
Can You Solve The Overlapping Squares Riddle?
Thanks to Ohad from Israel for suggesting this problem! A square with side length 5 has its corner at the center of a square with side length 4. The two squares overlap, and the overlapping region has one side equal to 3 as shown in the...
Curated Video
The Cats And Random Mouse Riddle. Tough Problem Solved With Markov Chains
Thanks to Josh for this problem! And thanks to Folke for emailing it to me! There are 7 doors in a line. A mouse starts in the middle at door 4. At doors 1 and 7 are cats. Every day the mouse moves one door left or right randomly, each...
Curated Video
Can You Solve The Boys And Girls Painting Rooms Riddle?
Thanks to Oladele from Nigeria for suggesting this problem! Team A has 4 girls and 7 boys. Team A takes 5 days to paint 4 rooms. Team B has 7 girls and 10 boys. Team B takes 4 days to paint 5 rooms. Team C has 8 girls and 5 boys. How...
Curated Video
Can You Solve The Three Erupting Geysers Riddle?
Thanks to Brian Galebach who created and sent me this problem! You arrive at a park where geysers A, B, and C erupt at intervals of precisely 2, 4, and 6 hours, respectively. Each started erupting independently at a random time in...
Curated Video
Seemingly Impossible 7th Grade Math Riddle - The Coded Table
Thanks to George who sent me this problem (created by 7th grade math teacher Ms. V)! There is a table in the video. The numbers in the first column are increased by the same percentage to give the numbers in the second column. But the...
Curated Video
Math Riddle From A Kenyan Bank
The Cooperative Bank of Kenya, one of Kenya's largest banks, tweeted out this problem. If 4 + 2 = 26, 8 + 1 = 79, 6 + 5 = 111, then what is 7 + 3 = ? My challenge: if 7 + 3 = z, solve for another pair of numbers x + y = z. Very few can...