00:00A brain teaser is a great tool to challenge one's ability to think creatively and rationally.
00:06That's why many companies like Apple, Microsoft, and Facebook are known for offering some tough
00:11interview riddles for their candidates.
00:13However, in recent years, business giants reportedly gave up this practice.
00:19Google even called riddles a waste of time because they don't predict anything about
00:23the candidate's future performance and serve only for the sake of feeding the interviewer's
00:27ego.
00:29But it's still curious to know whether you could crack those riddles, right?
00:33So let's find out!
00:36They say Microsoft and Amazon used this puzzle in their interviews.
00:41You're given eight identical-looking balls.
00:43One of them is heavier than the rest of the seven.
00:46You have simple mechanical scales and you can only make two measurements.
00:50Can you find the heavier ball?
00:58Let's name the balls 1 to 8.
01:00First, we should put the balls 1, 2, and 3 on the first side of the scales and balls
01:054, 5, and 6 on the second side.
01:08If these two groups have equal weight, it means that the heavier ball is either 7 or
01:128.
01:14In this case, all we need to do is weigh the remaining two balls and find out which is
01:18heavier.
01:20But let's talk about another scenario.
01:22Say one of the groups of three balls on the scales is heavier.
01:26The desired ball must be here.
01:28Now all you have to do is measure any two of these balls and reveal which one is heavier.
01:33If both balls have the same weight, then the desired ball is the one that remains unweighted.
01:38Today, Elon Musk reportedly doesn't interview each and every employee.
01:44But rumor has it that when he used to do that, he would ask this riddle.
01:49You're standing somewhere on the surface of Earth.
01:52You walk one mile south, then one mile west, and then one mile north.
01:56And you end up back at the same point where you started.
02:00Where are you?
02:07The most obvious reply is the North Pole.
02:10Congratulations, it's correct!
02:12But according to Musk's biographers, when he heard this answer, he would also ask, where
02:17else could you be?
02:19What do you say?
02:26Let's take a look at the circle of latitude near the South Pole that has a one-mile circumference.
02:32From any point on this circle, walking one mile west along this circle will bring you
02:36back to that same point.
02:38Therefore, any point a mile north of this circle of latitude is a possible solution
02:43to the riddle.
02:44There's another option.
02:46You might be anywhere that is five miles south of the equator.
02:50This way, your westerly and easterly routes rotate an equal amount around a latitude.
02:55Also, you might be a superhero who can teleport to any point anytime.
03:00But that's a whole different ballgame.
03:02In this case, SpaceX would probably hire you without even looking at your resume.
03:07Many job portals mention interview puzzles about crossing a river under various terms.
03:13Here's a tricky example of those riddles.
03:16Nine brothers live on an island.
03:18Their names are 1, 2, 3, 4, 5, 6, 7, 8, and 9.
03:25They need to cross a river.
03:27They have a single boat that can take them from one bank to the other.
03:31But it can handle a maximum of three brothers at a time.
03:34Also, the boat cannot sail on its own, so one brother must steer it.
03:39There's one more condition.
03:41The sum of the same numbers of the brothers crossing the river must be a total square
03:46number.
03:47What's the minimal number of trips required to send all the brothers across the river?
03:58On the first trip, send brothers 2, 5, and 9.
04:02The sum of these numbers is 16, which is 4 times 4.
04:05Then send 9 back.
04:07This will be the second trip.
04:09On the third trip, send 3, 4, and 9.
04:12Again, the sum of their numbers is 16, which meets the conditions perfectly.
04:17On the fourth trip, send 9 back.
04:19And on the fifth trip, send 1, 7, and 8.
04:23The sum of these numbers is 16 again.
04:26On the sixth trip, return 1 to the island.
04:29And finally, on the seventh trip, send 1, 6, and 9.
04:33The sum of these numbers totals 16, which is still a square number.
04:37So it takes at least 7 trips to send all the brothers across the river.
04:43Media reported that LinkedIn used the next riddle during its job interviews.
04:48You're in a room with 3 levers.
04:50There are 3 fountains in the next room.
04:53Each lever turns on one of the fountains.
04:55Your task is to figure out which lever controls which fountain.
04:59You can't see into one room from the other, and all the 3 fountains are off.
05:04You can inspect the other room only once.
05:07What would you do?
05:14Let's call the levers 1, 2, and 3.
05:17Leave the first lever off.
05:19Turn lever 2 on for 10 minutes.
05:21Now turn it off and quickly turn on lever 3.
05:25Go into the room.
05:26Find the fountain that is still wet but not working.
05:29That's the one controlled by lever 2.
05:31The one that's currently working is linked with lever 3.
05:35And the last one is linked with the first lever.
05:38This logical exercise from the 1960s is called the Wason Selection Task.
05:43Be careful, it's pretty tricky.
05:46Even math students fail to crack it.
05:50There are 4 cards.
05:51Each card has a letter on one side and a number on the other side.
05:55There's only one rule.
05:56Every card with the letter D on one side should have the number 3 on the opposite side.
06:02Can you guess which card or cards should be turned over to check if the rule has been
06:06followed?
06:14You need to check 2 cards, D and 7.
06:17Most people suggest choosing cards D and 3, but this answer is wrong.
06:21Let's go through each card to understand the logic.
06:25The rule says, if a card has D, it must have 3 on the other side.
06:30So we must check the first card to make sure there's a 3 on the opposite side.
06:35The second card shows the letter K.
06:38We know nothing about the other letters, so it doesn't matter what's on the other side,
06:42because neither case violates the rule, so we can skip it.
06:46We know that some cards with the 3 digits will have the letter D on the other side,
06:51but we don't know if that's true for all cards with 3s.
06:55So it makes no sense to check the third card.
06:58And finally, the fourth card.
07:00If we find the D letter on the other side, it would violate the rule, because there's
07:04a digit 7 on the opposite side.
07:07So we should check only these 2 cards.
07:12Here's another informal variation of the previous game.
07:15There are 4 cards representing different persons.
07:18One side shows their favorite beverage, and the other side, their age.
07:22The city has a rule that anyone drinking lemonade must be over 20 years old.
07:28Which cards do you need to turn over to make sure the rule is followed?
07:38You only need to check the lemonade card and the card with number 16.
07:42Obviously, you need to make sure the lemonade drinking is over 20, and you need to make
07:47sure that the 16-year-old person doesn't drink lemonade.
07:51The coffee person can be any age, and the 25-year-old can legally drink lemonade.
07:57Most people can solve this riddle pretty quickly, and that's curious because, in fact,
08:01this task is similar to the previous one.
08:05This famous puzzle was designed to challenge one's ability to reason and see patterns.
08:10Three ants are in the corners of an equilateral triangle.
08:14Each ant is moving in a random direction along the edges of the triangle.
08:18What's the probability that none of the ants collide with the triangle?
08:28There's a 50% possibility of the ants never colliding, and a 50% chance that at least
08:33two of them can meet.
08:35All the ants can move in either a clockwise or counterclockwise direction.
08:40This halves your first 50% chance of the never-meeting ants to a 25% chance.
08:47And here's an example of a tricky wording question.
08:50What two words, when combined, hold the most letters?
08:58Post and office.
09:04That's it for today.
09:05So, hey, if you pacified your curiosity, then give the video a like and share it with your
09:09friends.
09:10Or if you want more, just click on these videos and stay on the Bright Side!
Comments