Some people will instantly think of workplace campuses with napping nooks and Frisbee golf courses. Others will picture the smartest of the smart working on intensely complicated problems.
But these tech giants all hold something else in common as well. They’ve all used brainteaser questions in hiring interviews. And while they may not use them anymore, hundreds of other companies definitely took their lead and incorporated brainteasers into their interviews, too.
So let’s take a look at some of the trickiest Brain Teaser Interview Questions from Google, Apple and Facebook.
- Why Brainteasers?
- Google Brainteaser Questions
- 1 Why are manhole covers round?
- Makes perfect sense!
- 2 How many basketballs would fill up the cabin of a 747 jet?
- What about the stacking?
- 3 You have eight heavy blocks that look identical, except seven weigh the same, and one weighs slightly more. You have a balance, but you can only do two weightings.
- Or option 2…
- Apple Brainteaser Questions
- Facebook Brainteasers
- 6 How many times a day do a clock’s hands overlap?
- Let’s do it together…
- Oh, yeah… right.
- 7 You’re kidnapped and held at gunpoint. When your ransom doesn’t come in, the kidnapper puts two bullets next to each other in a 6-chambered gun, then spins the revolver. He holds the gun to your temple and pulls the trigger. CLICK!
- And if you do re-spin?
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- Final Thoughts
Most brainteaser questions have tricky answers, answers you need to actually work out mathematically, or answers that are painfully obvious but only in hindsight. Others can even have no real answer at all.
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This is actually quite a controversial subject. There are definitely arguments for and against using these types of questions in interviews, so here are just a few of them.
- To let the interviewer understand how a candidate thinks through difficult problems.
- They can demonstrate basic concrete logic skills like wordplay and basic calculations.
- It shows the interviewer how a candidate reacts to the pressure of tricky situations.
- They take up valuable interview time.
- Answering them doesn’t usually represent the type of work or problem-solving that jobs actually require.
- They may only make the interviewer feel smug by out-smarting the candidate.
Regardless of how you feel about brainteaser questions, they may just pop up in your next job interview. Since preparation is key, we’re going to look at some examples of these questions, including ones that have actually been used by Google, Facebook, and Apple. I’ll also talk about strategies for how to deal with these sorts of questions should they come up.
Get your brain ready – it’s time to get teased.
1 Why are manhole covers round?
There are many different ways to approach answering this question. You can maybe argue that there are manholes of other shapes around the world, including triangles and rectangles.
Play the history card and suggest that people have dug round holes since the dawn of humankind. You could even simply state that manhole covers are round because manholes are round.
Makes perfect sense!
But the most common answer to this question is that a round cover can never fall in the hole because no dimension’s shorter than the diameter of the hole.
Think about a square. Say it’s 2 x 2 feet long. The diagonal of that hole would be longer than 2 feet (the square root of the diagonal is equal to 2 squared + 2 squared, or √8, which equals 2.8). That means that if you turned the cover, it could fall through the hole and down onto someone’s head.
Of course, it’s probably never a good idea to leave the near balanced precariously near the hole anyway!
2 How many basketballs would fill up the cabin of a 747 jet?
There are all sorts of variations on this question, like golf balls in a school bus or beach balls in a skyscraper. The idea is always the same, however. Will you just spitball an answer that seems reasonable, or try to actually work the problem out?
An interviewer asking this question is probably looking at how you will approach the problem and reason it out. So here’s a possible answer:
“A basketball has a diameter of about 10 inches, so a radius of just 5 inches. That means it has a volume of about 523 cubic inches by the volume formula 4/3∏r3.
A 747 can seat about 350 people at 11 seats per row. That’s about 32 rows. If a row is about 3 feet long, That means the cabin is roughly 96 feet long, or 1152 inches. I am 6 foot tall and just hit my head on the overhead compartments, so I will estimate the cabin is 72 inches (6 foot x 12 inches/foot) high. I’m just going to guess the width is about 15 feet or 180 inches across.
That makes the cabin 1152 inches x 72 inches x 180 inches = 14,929,920 cubic inches.
Divided by the volume of a basketball, we get 14,929,920 / 523 = 28,546. This sounds surprising, but you could fit 28,546 basketballs into the cabin of a 747.
What about the stacking?
Of course, I didn’t account for stacking the balls. Because the balls are round, there’s always going to be some lost volume when they are stacked. Also, we didn’t say whether the balls were inflated or not. I’ve assumed they were, but if not, we’re going to have to worry less about volume and more about how much weight the 747 can carry!”
This sort of answer gives the interviewer a look at your mental processes. They can see if you’ve thought things through reasonably and also what possibilities could be taken into account.
3 You have eight heavy blocks that look identical, except seven weigh the same, and one weighs slightly more. You have a balance, but you can only do two weightings.
How can you find out which of the blocks is the heavier one?
It sounds easy at first. Weigh 4 and 4, and the heavier block will be on whichever side is heavier. Then split those blocks in half and weigh them again, and then – oops! You’d be left with two blocks and no more weighings left!
Instead, the only way to do it is to get the heavier block in a group of less than four from the first weighing. How? Weigh three blocks and three blocks on the balance, keeping two off to the side. If they balance, the block must be one of the two off to the side. Weigh those two, and you’ll find the heavy one.
Or option 2…
If the two sets of three blocks don’t balance, the heavier block is in, the heavier set of three. Take two of those three blocks and weigh them, while keeping one aside. If they balance, the one on the side is the heavy block. If they don’t balance, you’ll see which is heavier.
This question requires some actual problem-solving skills to be able to work it out. The problem is easy, but most people get stuck on the balance as forcing you to make only two groups and forget that whatever is left aside is still valuable.
4 You stand before two doors. One leads to the treasure, the other to certain death. Before each door is a guard. One always tells the truth; the other always lies.
What one question would you ask so that you can find the door to the treasure?
You may remember this famous problem from the 1983 movie Labyrinth. Well, there’s still a surefire way to answer this riddle. The correct question to ask is:
“Which door would the other guard say is the way to the treasure?”
If you ask the truth-teller, he’ll tell you the wrong door, since he will tell you truthfully what the liar will say. If you ask the liar, he’ll tell you the wrong door, since he will tell you falsely what the truth-teller will say. Either way, you get told the wrong door, so you’d just have to pick the other one.
If there’s another way to solve this riddle, I’d love to know it. But so far, Labyrinth and David Bowie have never steered me wrong.
5 There are three light bulbs in one room and three unlabeled switches in another room where you can’t see the lights.
How can you determine which switch controls which bulb without walking back and forth multiple times?
If you turn on one and check, you’re still short two answers. If you turn on two bulbs at the same time, there’s no way to know which is which… So how do you do it?
Here’s a remarkably simple solution: ask a friend to help! If the rules don’t say you can’t, then try to think outside the box, or outside the room in this case.
Another solution is to turn one switch on for a few minutes. Then turn it off and turn another switch on and go check the bulbs. The one you just turned on will be on. The one you never turned on will be off. And the third one will be off but still warm, so you’ll know it’s the one you turned on for a spell.
Unless it’s a power-saving LED bulb, those things are super-efficient!
6 How many times a day do a clock’s hands overlap?
You’ve got to be kidding, right? This is what they ask some of the brightest and best people in the world at interviews for some of the biggest companies around?
The minute hand goes around once an hour, and there are 24 hours in a day, so the answer is 24 times. Right? Except no.
Let’s do it together…
If you start at 12:00 am, the hands are overlapping, so you can count that as the first time. But by 1:00, the hands haven’t yet overlapped again. They won’t meet again until 1:05-ish, and then again at 2:10-ish. This means that they lose about five minutes every hour. That ends up making a big difference in the end.
Since 24 hours x 5 minutes is 120 minutes, you lose two full hours as the minute hand lags behind. That means they only overlap 22 times in a single day.
Oh, yeah… right.
This is one more of those questions where hindsight is 20/20. With this kind of question, an employer like Facebook wanted to see candidates looking at problems from a lot of different angles. And whether that’s a serious problem or even a silly riddle, this sort of perceptiveness may help you get hired by all sorts of companies out there.
7 You’re kidnapped and held at gunpoint. When your ransom doesn’t come in, the kidnapper puts two bullets next to each other in a 6-chambered gun, then spins the revolver. He holds the gun to your temple and pulls the trigger. CLICK!
He tells you he will pull the trigger again, but you can choose whether to spin the revolver again first or not. What will you choose? What’s the best way to stay alive?
Now, this is a serious situation that requires serious thought. Remember that the bullets are in two chambers next to each other in the revolver. You just missed one, but the next could end your life. That also means you just gave up a precious empty chamber. Does that mean you should spin again to get the empty chamber back?
There are six chambers with two bullets in them, so let’s think about the six different possibilities for where the bullets could be.
1 B B X X X X
2 B X X X X B
3 X X X X B B
4 X X X B B X
5 X X B B X X
6 X B B X X X
Here a “B” means a bullet in the chamber, “X” means empty. With situations 1 and 2, you wouldn’t be left alive to think about the problem, so we can scratch those out because they are obviously not the bullet configurations. So, you are left with only four options. If 3, 4, or 5 are right, then you’ll survive. Only option 6 will kill you.
This means you have a 1 in 4 chance of dying if you don’t re-spin the revolver, which is only 25%.
And if you do re-spin?
If you do re-spin, the six options are all on the table, and 1 and 2 will get you. That means a re-spin gives you a 2 in 6 chance of dying. That’s a 33% chance of biting the dust.
At first, I thought losing one empty chamber would mean that it would be better to re-spin, but the probabilities don’t bear that out. This is one of those questions that it would be great to have some time for as well as a pad and paper to help you puzzle it out.
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Looking For More Interview Advice?
Everyone gets nervous for interviews, so why not check out my advice on Why Do You Want To Work Here, How Would You Describe Yourself, What Makes You Unique, or how about How Do You Handle Stress, What Are You Most Proud Of, and Why We Should Hire You, as well as my Strengths And Weaknesses For Job Interviews, What Are Your Career Goals, and finally, the Best Questions To Ask In An Interview to help guide you.
Or you could try reading some excellent online guides such as Hiring Squirrels: 12 Essential Interview Questions to Uncover Great Retail Sales Talent, Get That Job!: The Quick and Complete Guide to a Winning Interview, and How to Answer Interview Questions: 101 Tough Interview Questions, or perhaps Amazing Interview Answers: 44 Tough Job Interview Questions with 88 Winning Answers, INTERVIEW with DESIRE and GET HIRED!: How to Ace the Interview, Sell Yourself & Get Your Dream Job for that final preparation.
It’s all about confidence…
You need to be confident in your interview; we recommend The Self Confidence Workbook, and The Confidence Gap: A Guide to Overcoming Fear and Self-Doubt, the Unstoppable Self Confidence, is also a great read, or maybe even the You Are a Badass: How to Stop Doubting Your Greatness and Start Living an Awesome Life, and The Confidence Code: The Science and Art of Self-Assurance all available online in 2023.
These weird and wild questions were popular with big tech in the 2000s, but most companies have found them to not be very useful. However, they set up a trend that continues to this day with many other companies who may still use brainteasers for their own reasons.
Usually, interviewers want to see how you would respond to different scenarios and challenges. They may not be looking for correct answers per se. Instead, they may be trying to find out how much of a systems thinker you are, how you work under pressure, or how good you are at pushing back your limitations.
So why not prep for a brainteaser or two by simply understanding some of the tricks they involve? Who knows, it might just help you get a job.
All the very best in answering those Brain Teaser Interview Questions!