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The Answers to 10 Tricky Job Interview Questions

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In an interview setting, even the most basic questions can feel nerve-racking. If you’ve ever drawn a blank when asked to talk about your hobbies, just imagine having to calculate the number of piano tuners in all of Chicago under that same kind of pressure.

Some competitive tech companies are notorious for asking hard-to-answer questions like this one. The interviewers who use them aren’t always looking for concrete figures, but rather they’re trying to gauge the candidates’ creativity and problem-solving skills. And while you may not know the exact number of piano tuners in Chicago off the top of your head, there is a “correct” line of thinking you can follow to find out.

These baffling brainteasers are becoming less common in the interview process (Google, one of the worst offenders, banned them a few years ago), but if you ever find yourself faced with one, here’s how to answer like you know what you’re talking about. 

1. HOW MANY GOLF BALLS CAN FIT INSIDE A SCHOOL BUS?

Here’s an example of a question where the interviewer isn’t expecting you to blurt out a specific figure with no context. There are lots of variables at play here, and the more questions you ask the better picture you’ll paint of your problem-solving process. “Is this a standard school bus?” “How large are the golf balls?” “Is this accounting for the seats inside?”

Once you figure out the dimensions of the school bus, you can calculate its volume into cubic inches then divide that number by the volume of a golf ball (2.5 cubic inches). The result would be the number of golf balls you could fit into the space when it’s completely empty (ignoring any gaps between the golf balls). To account for seats and other equipment, you have to estimate what percentage of the space is actually empty and multiply that by your original golf ball figure. 

If a standard school bus is 8 feet wide, 6 feet high, and 20 feet long, and 75 percent of the interior is unoccupied, then it could theoretically fit 495,000 golf balls (though if you're taking into account the gaps between the golf balls, it would be closer to 350,000). If you care more about being right than actually getting the job, feel free to shout out this number with no explanation. 

2. WHY ARE MANHOLE COVERS ROUND? 

This may seem like an open-ended question designed to evaluate the answerer’s personality, but the reasoning behind the manhole cover’s design is surprisingly straightforward. As we’ve explained here before, round covers are incapable of falling through manholes no matter how you position them. The ‘lip’ lining the rim of the opening ensures that the cover is always wider than the hole. Covers that are square, rectangular or oval in shape risk falling through if they’re inserted diagonally. Answering the question with these facts to back you up shows that you’re a logical thinkeror that you’ve spent too much time pondering your city's infrastructure.

3. HOW MUCH SHOULD YOU CHARGE TO WASH ALL THE WINDOWS IN SEATTLE?

Like the golf ball question, this problem can only be solved by making an educated guess at several variables. If Seattle consists of 10,000 city blocks with 600 windows per block, and the window washer spends five minutes per window while being paid a rate of $20 per hour, the answer would be approximately $10 million. On the other hand, the ability to keep things simple can sometimes be just as valuable as on-the-fly math skills. In that case, an answer like "$10 per window" (and you’d get paid 6 times as much!) would also suffice. 

4. HOW MANY PIANO TUNERS ARE THERE IN THE CITY OF CHICAGO?

If you were asked this question in a job interview, your natural response may be to laugh, cry, or perhaps flee the building as fast as possible. But with the help of some neat math tricks, you can actually come up with a pretty close approximation of the number using what little data’s available. 

This type of question is known as a Fermi Problem, and it can be solved by slightly overestimating and underestimating the figures using powers of ten with the assumption that they'll balance each other out in the end. To start you need to figure out the number of people living in Chicago. Instead of coming up with an exact number you can use 10 to the sixth, which equates to 1 million, to represent the population (the actual population of Chicago is just under 3 million, but we’re estimating!). Next, you need to estimate what portion of the population owns a piano. If it’s one out of every 100 people, that’s represented by 10 to the power of negative two, which when multiplied by ten to the sixth equals ten to the fourth (this may be starting to look complicated, but using the power of ten is actually how mathematicians are able to keep big numbers manageable). 

Ten to the fourth is the same as saying 10,000 pianos. To figure out the number of piano tuners based on that figure, you can assume that piano tuners are able to tune ten squared pianos each year. By dividing the number of pianos by the numbers of pianos tuned each year, you come up with the answer that there are ten squared, or 100 piano tuners in Chicago. 

Thanks to all the overestimations and underestimations cancelling each other out, you can count on ending up with a number that falls within one order of magnitude of the correct answer. Of course if you already have a Chicago phone book on hand, you could just count the number of piano tuners manually and find that there are actually around 81—but then you’d be missing out on all that fun math. 

See Also: 8 Illegal Interview Questions

5. HOW MANY TIMES DO A CLOCK’S HANDS OVERLAP IN A DAY?

Without giving the question much thought, you might automatically assume the answer to be 24, one overlap for each hour of the day. But, this being a list of tricky job interview questions, you can probably guess that this answer is wrong.

The only time the minute and the hour hand come together perfectly on the hour is at 12 o’ clock. After that the overlap occurs slightly after 1:05, then slightly after 2:10, etc. By the time the minute hand catches up to the hour hand the eleventh time, the hour hand has had enough of a head start that they don’t cross paths until 12 o’ clock, thus beginning the second twelve-hour cycle of the day. This means that there are only 11 times the two hands overlap every 12 hours, so they come together a total of 22 times during one day. 

Now try explaining all that coherently to a prospective employer while maintaining eye contact and an upbeat attitude. 

6. AN APPLE COSTS 40 CENTS, AN ORANGE COSTS 60 CENTS AND A GRAPEFRUIT COSTS 80 CENTS. HOW MUCH IS A PEAR?

There are several ways to tackle this question. One way is to look at the letters in the words themselves. If each vowel is worth 20 cents, then you can conclude that a pear would cost 40. If you were being read this question out loud as opposed to reading it, you might choose to interpret “pear” as “pair.” In that case a clever answer would be 80 cents for two apples, $1.20 for two oranges and $1.60 for two grapefruits. 

7. HOW MANY TRAFFIC LIGHTS ARE IN MANHATTAN?

Initially this question sounds similar to the piano tuner problem in that it can only be solved using the power of ten. While that’s probably the type of thinking interviewers are looking for, you could always take the easy route and pull up New York City’s Department of Transportation webpage (as of June 30, 2011, there were 2820 traffic signals in Manhattan).

8. HOW MANY BASKETBALLS CAN FIT IN THIS ROOM?

This is similar to the golf balls in a school bus problem, but this time the interviewee has the added advantage of being able to visually estimate the dimensions of the space that's being filled. You can go about solving it using the same straightforward math equations, or you can show off your creative thinking skills by asking some out-of-the-box questions first. A question like "Are the balls inflated or can I deflate them first?” demonstrates that you approach problems in a thoughtful way and are able to come up with smart solutions to achieve the best results.

9. WHAT DO WOOD AND ALCOHOL HAVE IN COMMON?

The way you answer this question shows potential employers how you’d go about finding common ground between two seemingly unrelated concepts. For this particular example, acceptable answers could include that both materials are flammable, or that methanol, a type of alcohol, is traditionally made from wood. 

10. HOW DO YOU MEASURE THE WEIGHT OF A BABY ELEPHANT WITHOUT A SCALE?

Being stuck with a baby elephant and no scale to weigh it with is quite a predicament, but the problem can be solved using a resourceful trick you may have learned about in high school. You can fill a large cylindrical glass vat with water not quite to the top, place a boat in the water and mark the water level. Then you put the elephant in the boat (which is probably harder than just buying a scale) and mark the new water level. Measure the difference between the two marks and with a little math you can easily calculate the weight of the elephant. Let’s hope that literally having to do this isn't part of the job description. 

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10 Bizarre Sesame Street Fan Theories
Zach Hyman, HBO
Zach Hyman, HBO

Sesame Street has been on the air for almost 50 years, but there’s still so much we don’t know about this beloved children’s show. What kind of bird is Big Bird? What’s the deal with Mr. Noodle? And how do you actually get to Sesame Street? Fans have filled in these gaps with frequently amusing—and sometimes bizarre—theories about how the cheerful neighborhood ticks. Read them at your own risk, because they’ll probably ruin the Count for you.

1. THE THEME SONG CONTAINS SECRET INSTRUCTIONS.

According to a Reddit theory, the Sesame Street theme song isn’t just catchy—it’s code. The lyrics spell out how to get to Sesame Street quite literally, giving listeners clues on how to access this fantasy land. It must be a sunny day (as the repeated line goes), you must bring a broom (“sweeping the clouds away”), and you have to give Oscar the Grouch the password (“everything’s a-ok”) to gain entrance. Make sure to memorize all the steps before you attempt.

2. SESAME STREET IS A REHAB CENTER FOR MONSTERS.

Sesame Street is populated with the stuff of nightmares. There’s a gigantic bird, a mean green guy who hides in the trash, and an actual vampire. These things should be scary, and some fans contend that they used to be. But then the creatures moved to Sesame Street, a rehabilitation area for formerly frightening monsters. In this community, monsters can’t roam outside the perimeters (“neighborhood”) as they recover. They must learn to educate children instead of eating them—and find a more harmless snack to fuel their hunger. Hence Cookie Monster’s fixation with baked goods.

3. BIG BIRD IS AN EXTINCT MOA.

Big Bird is a rare breed. He’s eight feet tall and while he can’t really fly, he can rollerskate. So what kind of bird is he? Big Bird’s species has been a matter of contention since Sesame Street began: Big Bird insists he’s a lark, while Oscar thinks he’s more of a homing pigeon. But there’s convincing evidence that Big Bird is an extinct moa. The moa were 10 species of flightless birds who lived in New Zealand. They had long necks and stout torsos, and reached up to 12 feet in height. Scientists claim they died off hundreds of years ago, but could one be living on Sesame Street? It makes sense, especially considering his best friend looks a lot like a woolly mammoth.

4. OSCAR’S TRASH CAN IS A TARDIS.

Oscar’s home doesn’t seem very big. But as The Adventures of Elmo in Grouchland revealed, his trash can holds much more than moldy banana peels. The Grouch has chandeliers and even an interdimensional portal down there! There’s only one logical explanation for this outrageously spacious trash can: It’s a Doctor Who-style TARDIS.

5. IT’S ALL A RIFF ON PLATO.

Dust off your copy of The Republic, because this is about to get philosophical. Plato has a famous allegory about a cave, one that explains enlightenment through actual sunlight. He describes a prisoner who steps out of the cave and into the sun, realizing his entire understanding of the world is wrong. When he returns to the cave to educate his fellow prisoners, they don’t believe him, because the information is too overwhelming and contradictory to what they know. The lesson is that education is a gradual learning process, one where pupils must move through the cave themselves, putting pieces together along the way. And what better guide is there than a merry kids’ show?

According to one Reddit theory, Sesame Street builds on Plato’s teachings by presenting a utopia where all kinds of creatures live together in harmony. There’s no racism or suffocating gender roles, just another sunny (see what they did there?) day in the neighborhood. Sesame Street shows the audience what an enlightened society looks like through simple songs and silly jokes, spoon-feeding Plato’s “cave dwellers” knowledge at an early age.

6. MR. NOODLE IS IN HELL.

Can a grown man really enjoy taking orders from a squeaky red puppet? And why does Mr. Noodle live outside a window in Elmo’s house anyway? According to this hilariously bleak theory, no, Mr. Noodle does not like dancing for Elmo, but he has to, because he’s in hell. Think about it: He’s seemingly trapped in a surreal place where he can’t talk, but he has to do whatever a fuzzy monster named Elmo says. Definitely sounds like hell.

7. ELMO IS ANIMAL’S SON.

Okay, so remember when Animal chases a shrieking woman out of the college auditorium in The Muppets Take Manhattan? (If you don't, see above.) One fan thinks Animal had a fling with this lady, which produced Elmo. While the two might have similar coloring, this theory completely ignores Elmo’s dad Louie, who appears in many Sesame Street episodes. But maybe Animal is a distant cousin.

8. COOKIE MONSTER HAS AN EATING DISORDER.

Cookie Monster loves to cram chocolate chip treats into his mouth. But as eagle-eyed viewers have observed, he doesn’t really eat the cookies so much as chew them into messy crumbs that fly in every direction. This could indicate Cookie Monster has a chewing and spitting eating disorder, meaning he doesn’t actually consume food—he just chews and spits it out. There’s a more detailed (and dark) diagnosis of Cookie Monster’s symptoms here.

9. THE COUNT EATS CHILDREN.

Can a vampire really get his kicks from counting to five? One of the craziest Sesame Street fan theories posits that the Count lures kids to their death with his number games. That’s why the cast of children on Sesame Street changes so frequently—the Count eats them all after teaching them to add. The adult cast, meanwhile, stays pretty much the same, implying the grown-ups are either under a vampiric spell or looking the other way as the Count does his thing.

10. THE COUNT IS ALSO A PIMP.

Alright, this is just a Dave Chappelle joke. But the Count does have a cape.

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17 Things to Know About René Descartes
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The French polymath René Descartes (1596-1650) lived after the Renaissance, but he personified that age's interest in mathematics, philosophy, art, and the nature of humanity. He made numerous discoveries and argued for ideas that people continue to grapple with. (His dualist distinction between mind and the brain, for example, continues to be debated by psychologists.) Get to know him better!

1. NOBODY CALLED HIM RENÉ.

Descartes went by a nickname and often introduced himself as “Poitevin” and signed letters as “du Perron.” Sometimes, he went so far to call himself the “Lord of Perron.” That’s because he had inherited a farm from his mother’s family in Poitou, in western France.

2. SCHOOL MADE HIM FEEL DUMBER.

From the age of 11 to 18, Descartes attended one of the best schools in Europe, the Jesuit College of Henry IV in La Flèche, France. In his later work Discourse on the Method, Descartes wrote that, upon leaving school, “I found myself involved in so many doubts and errors, that I was convinced I had advanced no farther in all my attempts at learning, than the discovery at every turn of my own ignorance."

3. HIS DAD WANTED HIM TO BE A LAWYER.

Descartes’s family was chock-full of lawyers, and the budding intellectual was expected to join them. He studied law at the University of Poitiers and even came home with a law degree in 1616. But he never entered the practice. In 1618, a 22-year-old Descartes enlisted as a mercenary in the Dutch States Army instead. There, he would study military engineering and become fascinated with math and physics.

4. HE CHANGED CAREER PATHS THANKS TO A SERIES OF DREAMS.

In 1618, the Emperor of the Holy Roman Empire, Ferdinand II, attempted to impose Catholicism on anybody living within his domain. The result of this policy would be the Thirty Years' War. It would also prompt Descartes, a Catholic, to switch allegiances to a Bavarian army fighting for the Catholic side. But on his travels, he stopped in the town of Ulm. There, on the night of November 10, he had three dreams that convinced him to change his life’s path. “Descartes took from them the message that he should set out to reform all knowledge,” philosopher Gary Hatfield writes in the Stanford Encyclopedia of Philosophy.

5. HE COULD BE EASILY DISTRACTED BY BRIGHT AND SHINY OBJECTS.

In 1628, Descartes moved to the Netherlands and spent nine months doggedly working on a theory of metaphysics. Then he got distracted. In 1629, a number of false suns—called parhelia, or “sun dogs”—were seen near Rome. Descartes put his beloved metaphysics treatise on the back burner and devoted his time to explaining the phenomenon. It was a lucky distraction: It led to his work The World, or Treatise on Light.

6. HE LAID THE GROUNDWORK FOR ANALYTIC GEOMETRY ...

In 1637, Descartes published his groundbreaking Discourse on the Method, where he took the revolutionary step of describing lines through mathematical equations. According to Hatfield, “[Descartes] considered his algebraic techniques to provide a powerful alternative to actual compass-and-ruler constructions when the latter became too intricate.” You might have encountered his system in high school algebra: They’re called Cartesian coordinates.

7. ... AND THE REST OF WESTERN PHILOSOPHY.

Everybody knows Descartes for his phrase Cogito, ergo sum (which originally appeared in French as "Je pense, donc je suis"), or "I think, therefore I am." The concept appeared in many of his texts. To understand what it means, some context is helpful: At the time, many philosophers claimed that truth was acquired through sense impressions. Descartes disagreed. He argued that our senses are unreliable. An ill person can hallucinate. An amputee can feel phantom limb pain. People are regularly deceived by their own eyes, dreams, and imaginations. Descartes, however, realized that his argument opened a door for "radical doubt": That is, what was stopping people from doubting the existence of, well, everything? The cogito argument is his remedy: Even if you doubt the existence of everything, you cannot doubt the existence of your own mind—because doubting indicates thinking, and thinking indicates existing. Descartes argued that self-evident truths like this—and not the senses—must be the foundation of philosophical investigations.

8. HE'S THE REASON YOUR MATH TEACHER MAKES YOU CHECK YOUR WORK.

Descartes was obsessed with certainty. In his book Rules for the Direction of the Mind, “he sought to generalize the methods of mathematics so as to provide a route to clear knowledge of everything that human beings can know,” Hatfield writes. His advice included this classic chestnut: To solve a big problem, break it up into small, easy-to-understand parts—and check each step often.

9. HE LIKED TO HIDE.

Descartes had a motto, which he took from Ovid: “Who lives well hidden, lives well.” When he moved to the Netherlands, he regularly changed apartments and deliberately kept his address a secret. Some say it's because he simply desired privacy for his philosophical work, or that he was avoiding his disapproving family. In his book titled Descartes, philosopher A. C. Grayling makes another suggestion: "Descartes was a spy."

10. HE WASN'T AFRAID OF CRITICS. IN FACT, HE RE-PUBLISHED THEM.

When Descartes was revising his Meditations on First Philosophy [PDF], he planned to send the manuscript to “the 20 or 30 most learned theologians” for criticism—a sort of proto-peer review. He collected seven objections and published them in the work. (Descartes, of course, had the last word: He responded to each criticism.)

11. HE COULD THROW SHADE WITH THE BEST OF THEM.

In the 1640s, Descartes’s pupil and friend Henricus Regius published a broadsheet that distorted Descartes’s theory of the mind. (Which, put briefly, posits that the material body and immaterial mind are separate and distinct.) The two men had a falling out, and Descartes wrote a rebuttal with a barbed title that refused to even acknowledge Regius’s manifesto by name: It was simply called “Comments on a Certain Broadsheet.”

12. HE NEVER BELIEVED MONKEYS COULD TALK.

There’s a “fun fact” parading around that suggests Descartes believed monkeys and apes could talk. He believed no such thing. According to the Stanford Encyclopedia of Philosophy, Descartes denied that animals were even conscious, let alone capable of speech. The factoid comes from a misreading of a letter Descartes had written in 1646, in which he attributed the belief to “savages.”

13. HE TOTALLY HAD THE HOTS FOR CROSS-EYED WOMEN.

In a letter to Queen Christina of Sweden, Descartes explained that he had a cross-eyed playmate as a child. “I loved a girl of my own age ... who was slightly cross-eyed; by which means, the impression made in my brain when I looked at her wandering eyes was joined so much to that which also occurred when the passion of love moved me, that for a long time afterward, in seeing cross-eyed women, I felt more inclined to love them than others.”

14. WHEN HE MET BLAISE PASCAL, THEY GOT INTO AN ARGUMENT ... ABOUT VACUUMS.

In 1647, a 51-year-old Descartes visited the 24-year-old prodigy and physicist Blaise Pascal. Their meeting quickly devolved into a heated argument over the concept of a vacuum—that is, the idea that air pressure could ever be reduced to zero. (Descartes said it was impossible; Pascal disagreed.) Later, Descartes wrote a letter that, depending on your translation, said that Pascal had “too much vacuum in his head.”

15. HIS WORK WAS BANNED BY THE CATHOLIC CHURCH.

Back in the late 1630s, the theologian Gisbert Voetius had convinced the academic senate of the University of Utrecht to condemn the philosopher’s work. (Descartes was Catholic, but his suggestion that the universe began as a “chaotic soup of particles in motion,” in Hatfield's words, was contrary to orthodox theology.) In the 1660s, his works were placed on the church’s Index of Prohibited Books.

16. HE REGULARLY SLEPT UNTIL NOON (AND TRYING TO BREAK THE HABIT MIGHT HAVE KILLED HIM).

Descartes was not a morning person. He often snoozed 12 hours a night, from midnight until lunchtime. In fact, he worked in bed. (Sleep, he wisely wrote, was a time of “nourishment for the brain.”) But according to the Journal of Historical Neuroscience, he may have had a sleep disorder that helped end his life. A year before his death, Descartes had moved to Stockholm to take a job tutoring Queen Christina, a devoted early-riser who forced Descartes to change his sleep schedule. Some believe the resulting sleep deprivation weakened his immune system and eventually killed him.

17. HIS SKELETON HAS TRAVELED FAR AND WIDE.

Descartes died in Stockholm in 1650 and was buried outside the city. Sixteen years later, his corpse was exhumed and taken to Paris. During the French Revolution, his bones were moved to an Egyptian sarcophagus at the Museum of French Monuments. Decades later, when plans were made to rebury Descartes in an abbey, officials discovered that most of his bones—including his skull—were missing. Shortly after, a Swedish scientist discovered a newspaper advertisement attempting to sell the polymath’s noggin [PDF]. Today, his head is in a collection at the Musée de l’Homme in Paris.

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