Search Results: "MindYourDecisions"
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05:39
Can You Solve A 5th Grade Problem From China? Find The Area Of ABCD
520 views / 0 likes  addedThanks to Eric from Miami for suggesting this problem and sending a solution! The diagram shows a quadrilateral ABCD with the values for some angles and the length of AB. Can you figure out the area of ABCD? Subscribe: https://www.youtube.com/user/MindYou

08:51
The Viral Balloon Puzzle  The REAL Answer Explained (Using Ph.D. Level Math)
431 views / 0 likes  addedThey say only geniuses can solve this puzzle, and this time they are correct. Thanks to all patrons! Special thanks to: Shrihari Puranik Yildiz Kabaran Kyle My blog post for this video https://wp.me/p6aMk82U Sources https://puzzling.stackexchange.com/que

03:21
Can You Solve A Puzzle That Fooled Richard Feynman?
390 views / 0 likes  addedWhat is the radius of the circle, in simplest terms involving a, b, and c? I read that even the great mind Richard Feynman made a mistake. Watch the video to learn the common mistake and what the correct answer is. Source Feynman story http://web.media.mi

05:48
What Is The Area? "You Should Be Able To Solve This"
249 views / 0 likes  addedThanks to Reio in Romania for emailing me this fun problem! What is the area? This puzzle was shared with the tagline "you should be able to solve this." Solution to 5th grade Chinese challenge problem https://youtu.be/OuJQaxZvlYs My blog post for this vi

05:52
Can You Solve The "MEANEST" SAT Test Question Ever?
411 views / 0 likes  addedOn the SAT exam, you have about 2 minutes to read and solve each math question. This one about averages can send you in a loop, unless you approach it systematically. In the video I also explain a shortcut to help you solve this type of problem quickly. S

03:00
Multiply Numbers By Drawing Lines
406 views / 0 likes  addedGow to multiply numbers by drawing lines. Get the Multiply By Lines Book! https://www.amazon.com/gp/product/1500866148/ If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecisions Connect on social media. I update each s
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03:51
Can You Solve This MIT Admissions Question? Geometry Problem, 1869
598 views / 0 likes  addedThe 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 the hypotenuse divid

06:18
Can You Solve The Diluted Wine Puzzle?
408 views / 1 likes  addedA servant has a method to steal wine. He removes 3 cups from a barrel of wine and replaces it with 3 cups of water. The next day he wants more wine, so he does the same thing: he removes 3 cups from the same barrel (now with diluted wine) and replaces it

06:24
Can You Solve The Missing Sock Puzzle?
346 views / 0 likes  addedA statistician keeps a simple wardrobe. He only purchases pairs of black socks and white socks, and he keeps all of the socks in a pile in the drawer. Recently one of the socks was lost in the laundry. The socks have a mathematical property. If you select

03:16
Can You Solve This 8th Grade Geometry Problem? 75% Got The Wrong Answer
421 views / 0 likes  addedWhat is angle A in the starshaped figure? This problem appeared on the 1999 AMC 8 test (intended for 8th grade students in the US). Approximately 75% of testtakers did not mark the correct response. Can you figure it out? Watch the video for a solution.

05:27
Can You Solve The MindBending SelfCounting Sentence Riddle?
627 views / 0 likes  added"In this sentence, the number of occurrences of the digit 0 is __, of the digit 1 is __, of the digit 2 is __, of the digit 3 is __, of the digit 4 is __, of the digit 5 is __, of the digit 6 is __, of the digit 7 is __, of the digit 8 is __, and of the d

04:13
Can You Solve This Grade 12 Geometry Problem From Australia? The Marshmallow Chocolate Puzzle
459 views / 0 likes  addedA marshmallow has the shape of a cylinder with diameter 5 and height 3. A dessert is made with 24 marshmallows: there are two stacked layers of marshmallows, and each layer has 3 rows of 4 marshmallows. The gaps between the marshmallows are filled with ch

07:49
Can You Solve The Viral 9 = 72 Puzzle? The Correct Answer Explained
647 views / 0 likes  addedThis problem has been shared millions of times on Twitter/Facebook with the claim "99% fail" to solve it and that only a genius could find the correct answer. If 9 = 72, 8 = 56, 7 = 42, 6 = 30, 5 = 20, then 3 = ? In this video I explain what many people b

04:30
Adults Are Arguing About This 3rd Grade Math Problem
513 views / 0 likes  added"If Sue runs around the track twice, and John runs around the track four times more than Sue, how many times does John run around the track?" This problem was given to 3rd graders. A parent disagreed with the answer the teacher was marking. After it was p

07:47
Can You Solve The Probability The Newborn Is A Boy? Many Fail This Interview Question
521 views / 0 likes  addedThis problem has been asked in job interviews. On the morning of January 1, a hospital nursery has 3 boys and some number of girls. That night, a woman gives birth to a child, and the child is placed in the nursery. On January 2, a statistician conducts a

02:45
The Day After Tomorrow Is Yesterday Riddle. Can You Solve It?
423 views / 0 likes  addedThis puzzle is popular on Facebook and many other sites. "When the day after tomorrow is yesterday, then today will be as far from Wednesday as today was from Wednesday when the day before yesterday was tomorrow. What day is today?" Can you solve this tri

09:11
Can You Solve The Rectangle Ratio Puzzle? The Surprising Answer
527 views / 0 likes  addedStart with a unit square (a rectangle with both sides equal to 1, call it R1). Attach a rectangle of area 1 to its right side, then attach a rectangle of area 1 to its top. The border of this new shape is another rectangle, call it R2. We can repeat the p

03:54
What's The Best Soup Can Size? The Optimal Cylinder Puzzle
443 views / 0 likes  addedA cylindrical can with volume V can be made in different ways. The cylinder can be wide and short (large radius and small height), or it can be narrower and taller (small radius and larger height). Which shape uses the least material? That is, which can h

03:48
Can You Solve This Harvard Admissions Question? Algebra Problem, 1869
554 views / 0 likes  addedThe Harvard admissions exam in 1869 included this algebra problem: "A man bought a watch, a chain, and a locket for $216. The watch and locket together cost three times as much as the chain, and the chain and locket together cost half as much as the watch

05:57 Popular
Can You Solve This 6th Grade Geometry Problem From Singapore? The Area Of A "Claw"
736 views / 1 likes  addedThis problem was given to Primary 6 (age 1112) students in Singapore. What is the area of the shaded region in the video, which consists of the region bounded by 4 quarter circles in a 3x3 grid of squares, and each square has a side length of 4? The shad

07:40
Can You Solve The 21 Flags Game From Survivor?
455 views / 0 likes  addedContestants on the TV show "Survivor" faced off in a series of challenges for a grand prize of $1 million. Most of the challenges were physical like hiking many miles or diving underwater. But one challenge was mathematical. The game had 21 flags and cont

11:27 Popular
Can You Solve The Viral 11x11 = 4 Puzzle? The Correct Answer Explained
1,052 views / 1 likes  addedIf 11x11=4 and 22x22=16, what is 33x33=? This puzzle has been shared with the claim that only geniuses can solve it. It has gotten millions of views on the internet and Facebook as people have debated the correct answer. In this video I present what many

07:39
Can You Solve The Alien Extinction Riddle? Hard Job Interview Question
512 views / 0 likes  addedA single alien lands on Earth. Every day after that, each alien on Earth undergoes a transformation, which could be any of the four equally likely events: (a) the alien dies, (b) the alien does nothing, (c) the alien replicates itself (2 aliens total), (d

11:57
The Wallis Formula For π
335 views / 0 likes  addedStart with the pair of fractions (2/1)(2/3). Now increment each number by 2 to get the pair of fractions (4/3)(4/5). Repeat this to get the next pair, and repeat this infinitely many times. If you then multiply all the fractions, you get a marvelous value

02:06 Popular
Can You Solve The Viral Matchstick Puzzle 6 + 4 = 4?
1,093 views / 0 likes  addedCan you fix 6 + 4 = 4 by moving 1 matchstick? This problem has gone viral on Facebook, with one post having over 400,000 shares. The ground rules are you cannot break a stick, it should be an equality (=), and you have to use 7segment numbers (the block

02:51 Popular
The Horse Horseshoe Boots Viral Algebra Problem  The Correct Answer Explained
920 views / 1 likes  addedA lot of people are arguing over the correct answer to this algebra problem involving horses, horseshoes, and boots. A Facebook post with this problem has over 500,000 comments. Can you figure it out? In this video I explain the correct answer. Blog post:

05:33
What is 6÷2(1+2) = ? The Correct Answer Explained
615 views / 0 likes  addedWhat is 6÷2(1+2) = ? This problem went viral and generated millions of comments on Facebook, Twitter, YouTube and social media sites. I explain how to get the correct answer by using the modern interpretation of the order of operations. I also explain how
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07:25
Can You Solve The Race To December 31 Riddle?
443 views / 0 likes  addedHere's a fun game you can play with another person. The game starts on January 1. Each of two players takes turns calling out another date. The new date has to be a later date in the year with either the same month OR the same day (from January 1, a playe

08:05
Can You Solve The Hardest Easy Geometry Problem?
675 views / 1 likes  addedIn 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 work out. Can you

05:55
"Impossible" Logic Puzzle  How Many Liars Are At The Party?
480 views / 0 likes  addedA party has 100 people who are either liars are truth tellers. Liars always lie and truth tellers always say the truth. After the party you ask each person, "How many truth tellers did you shake hands with?" Each person gives a different answer from 0 to

06:01 Popular
Can You Solve The Viral 1 + 4 = 5 Puzzle? The Correct Answer Explained
5,084 views / 0 likes  addedThis problem was shared on Facebook with the claim that only one in a thousand could figure it out. It went viral and generated over 3 million comments. Here is the problem. If 1 + 4 = 5, 2 + 5 = 12, 3 + 6 = 21, what is 8 + 11 = ? This video presents what

08:19
Can You Solve The Spies Sharing Secrets Puzzle?
369 views / 1 likes  addedAfter a successful mission, each of N spies obtains a unique secret. By protocol, the spies share secrets by a series of phone calls between 2 spies at a time. During a call, a spy can share all the secrets the knows, including secrets learned from previo

04:53
Can You Solve The Friendship Riddle?
303 views / 0 likes  addedIn a group of 6 people, you might find that some people are friends on Facebook, or you might find out that no one is friends on Facebook. Show that there is always a group of 3 people in which either: (a) all 3 people are mutual friends or (b) the 3 peop

10:20
SURPRISING Coin Flipping Probability  Flips To HH Versus HT
314 views / 0 likes  addedWhat is the expected number of coin flips until you get two heads in a row (HH)? What is the expected number of coin flips until you get a heads followed by a tails (HT)? The video presents the solution and an intuitive explanation for this probability ri

09:50 Popular
Can You Solve This 6th Grade Geometry Problem From China?
869 views / 1 likes  addedWhat is the total area of the red spots? The diagram involves a rectangle with dimensions of 10 and 20. Inside the rectangle one of its diagonals is connected. There are two circles of equal size that are tangent to each other and the rectangle. The video
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06:24
Can You Solve The Chameleon Riddle?
565 views / 0 likes  addedA museum has 13 blue, 15 red, and 17 green chameleons. Whenever two chameleons of different colors meet, they both change into the color of the other chameleon (if blue and red met, for example, they would both turn green). As the chameleons mingle, is it

07:21
Can You Solve The Magical Pond Puzzle?
456 views / 1 likes  added(Same video with music: https://youtu.be/nFGpk0ZpRk) You visit a shrine that has 3 temples. Before each temple, you have to swim in a magical pond. Your path is pondtemple1pondtemple2pondtemple 3. Each time you swim, the pond magically triples the n

05:26
Can You Solve The Red Ball Lottery Puzzle?
391 views / 0 likes  added(Same video without the music: https://youtu.be/sz5oLEpc8xE) This problem involves 100 red balls, 100 blue balls, and 2 urns. First you distribute all the balls between the 2 urns, placing at least 1 ball in each urn. Next, you select an urn at random, an

01:49
This Matchstick Puzzle Is
463 views / 1 likes  addedThis classic matchstick/toothpick puzzle is making the rounds because it is supposedly "extremely hard" for adults. Can you make 3 squares by moving 3 matchsticks? You cannot break any of the sticks, the resulting squares must be of equal size, and each t
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13:40
BEST Way To Play Memory (Card Game)  WIN Using Math
648 views / 0 likes  addedThe card game of memory (aka concentration) is a children's game to test visual recall. Strategically you can figure out the best move by doing probability calculations. This video explains the best possible way to play the game mathematically. You can le
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03:17
Can YOU Solve It? This Question Stumped 75% Of PhD Economists
374 views / 0 likes  addedIntroductory economics courses cover the concept of an opportunity cost. Can you figure out the opportunity cost for the problem in the video? This video presents a question that surprisingly more than 75% of PhD economists did not answer correctly. Paper

05:57
How To Split A Cake Fairly Using Math
430 views / 0 likes  addedHow can 2 people split up a cake, knowing that each person wants to get a larger piece than the other? What about 3 people, or even N people? This is an example of a fair division problem from game theory. There are many cakecutting algorithms to produce
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02:23
This SAT Math Question Has A Mistake
400 views / 0 likes  addedThis question appeared on the October 1980 SAT exam. Like all questions, it was supposed to have exactly one correct answer. However the testmakers made a mistake. Can you figure out what they did wrong? Blog post (text explanation): http://wp.me/p6aMk4

03:25 Popular
Can You Solve This? AA + BB + CC = ABC
1,259 views / 0 likes  addedIf AA + BB + CC = ABC, what are the values of A, B, and C? All the digits are distinct and positive. Watch the video for a solution. Blog (text explanation): http://wp.me/p6aMk4Cm If you like my videos, you can support me at Patreon: http://www.patreon.c

04:22 Popular
Impossible Algebra Problem
843 views / 0 likes  addedThis problem is making the rounds. Can you place numbers in the four boxes so all the equations are true? Blog post (text/image explanation): http://wp.me/p6aMk4up If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecis

03:31
How Logical Are You? The Irrationality Illusion Tricks Most
584 views / 0 likes  addedThis video relates a cognitive bias ("irrational" decision) to an optical illusion (picture at 1:45). For more, check out my new book, "The Irrationality Illusion: How to Make Smart Decisions And Overcome Bias" http://amzn.to/1o3FaAg Blog post (text and i

04:42
How Warren Buffett Tried To Trick Bill Gates In A Dice Game
383 views / 0 likes  addedWarren Buffett once challenged Bill Gates to a dice game similar to this one. How would you play the game? Blog post (text explanation) http://wp.me/p6aMk4ro Source The dice numbers and the story are described at Microsoft Research's website for nontran

07:10
TOUGH Interview Question  Ways To Give 11 Coins To 3 People
376 views / 0 likes  addedHow many ways can you divide 11 coins to 3 people? How many ways are there if each person has to get at least 1 coin? This puzzle is an example of a technical interview question. The video demonstrates the solution, which indicates the number of nonnegat

15:15
Moving Faster Than The Speed Of Light? Special Relativity Velocity Addition Formula
434 views / 0 likes  addedIf train A is moving towards train B, and each train moves at 75% the speed of light (relative to the ground), will an observer on train A think that train B is moving at 150% the speed of light? But nothing moves faster than the speed of light, so what i

06:57
When Is Christmas? Mentally Convert Date To Day Of The Week
337 views / 0 likes  addedJanuary 1, 2016 is a Friday. When will Christmas be in 2016? What about Christmas in 2055? You can do this in your head! Blog post (text explanation): http://wp.me/p6aMk4qQ Doomsday Rule (previous video): https://www.youtube.com/watch?v=UsStBxY9STw Calcu

02:57
Viral Facebook Math Problem
699 views / 1 likes  addedThis problem has over 2 million comments on Facebook and is getting coverage in mainstream media and blogs. Can you figure out this Facebook fruit algebra puzzle involving apples, bananas, and coconuts? The video presents what many people consider to be t

01:18
Can You Make 4 Triangles From 6 Matches?
639 views / 0 likes  addedCan you use 6 matches to make 4 triangles of equal size and equal shape? This is harder than it sounds! Give it a try before watching the video for a solution. If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecisions

07:52
Find The 10 Digit Number Classic Puzzle And Solution
477 views / 0 likes  addedI'm thinking of a 10 digit number that uses the each digit 0 to 9 exactly once and where the number formed by the first n digits is divisible by n. What could my number be? The video explains how to find the answer using tests for divisibility. Blog post:

06:24 Popular
The Seemingly Impossible Escape Logic Puzzle
844 views / 0 likes  addedAn evil logician takes Alice and Bob captive. They have a chance to escape if they can deduce the total number of trees in the prison. Can they figure it out? Source of puzzle wu: riddles forum https://www.ocf.berkeley.edu/~wwu/cgibin/yabb/YaBB.cgi?board

01:57 Popular
I Will Read Your Mind  Math Magic Trick
751 views / 1 likes  addedPick a 2 digit number. Got it? Now and add up the digits. Subtract that from your original number. Look up the resulting number in the table. Can I figure out the symbol you are looking at? This video predicts your symbol and explains why this math trick
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03:33
Can You Solve This Intelligence Test? Viral Facebook Puzzle
443 views / 0 likes  addedIf 6 + 4 = 210, and 9 + 2 = 711, what is the rule to combine numbers? This "intelligence test" has been shared more than 3 million times on Facebook. On Twitter people claim solving it means you have an IQ of more than 150 (genius level). In this video I

04:52
Can You Solve The Two Rope Puzzle?
434 views / 0 likes  addedYou have two ropes and a lighter. Each rope burns in 60 minutes, but the ropes do not burn at a constant rate. How can you measure 45 minutes by burning the ropes? Some of you might have heard this problem before. If so, try this variation: how can you me

03:09
Can You Solve The Marriage Logic Problem? 80% Fail
410 views / 0 likes  addedSurveys have found 80 percent get this logic problem wrong. Alice is looking at Bob, and Bob is looking at Charlie. Alice is married; Charlie is not. Is a married person looking at an unmarried person? Answer choices are A) Yes, B) No, and C) Cannot be de

02:57
Can You Solve This Crazy Equation? Ramanujan's Radical Brain Teaser
470 views / 0 likes  addedIn 1911, Srinivasa Ramanujan posed this problem involving an infinite nested radical (a neverending expression that has square roots inside of square roots). Can you figure out how to simplify the equation? The video presents an intuitive solution. Techn

08:27
Can You Solve The 3 Cards Riddle?
426 views / 0 likes  addedThere are 3 cards in this problem. One card is blue on both sides, another is red on both sides, and the last is red on one side and blue on the other. The cards are put in a bag and I pick one at random. Without looking at the colors on the card, I place

05:09
Can You Solve The Snake Eyes Probability Riddle?
504 views / 0 likes  addedYou close your eyes and roll a pair of dice. The casino dealer announces that at least one of the rolls is showing a 1.What is the probability that both dice are showing a 1? Watch the video for the solution. (Snake eyes is a term for rolling a pair of 1s

02:37
Adults Stumped By Maths Questions For 15 Year Olds. Can You Solve Them?
469 views / 0 likes  addedHow hard are math tests? A survey asked 2,000 UK adults to answer sample GCSE test questions intended for 15 year old students. On average, the survey questions were missed by about 40% of adults. Can you solve them? The video presents 2 questions that ma

04:13
Adults Stumped By Geometry Problems For 10 Year Olds. Can You Solve Them?
521 views / 0 likes  addedThese homework problems were given to 10 year old children (Year 5) in England (Glossop, Derbyshire) and they were posted to Facebook when some adults found them to be difficult. One person claimed the problems were impossible to solve. Can you figure the

03:28
Flower Math Problem  Adults Stumped By Question For Kids In China
671 views / 2 likes  addedThis problem is said to come from a test given to a Chinese kindergarten class (5 year olds). It was posted online and caused a lot of debate as adults were stumped about the correct answer, some saying it is impossible. Can you figure it out? This video
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