My Nightmare Interviews With Google
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One of the unofficial interviewers (at 24 year old MIT engineer working as an email marketer) challenged me with the question "How many barbers are in San Francisco?" We proceeded to map it out the analytical process on the whiteboard. He wanted to see formulas to understand how I would arrive at the answer.
It was a stupid, impossible question. In a similar way to this girl's experience, he jabbed repeatedly critiquing my logic.
He wrote me later to explain that he posed the same question to his girlfriend, an MIT engineer herself, and she couldn't come up with an answer. Neither could he.
They offered me the job and I declined solely based on this guy and his misguided, silly behavior. I would have hated to work with him.
When a company misguidedly challenges potential employees in this way it hurts the quality of its hires. Sure, Google can afford to be picky but does it really need an engineer in a Product Marketing role? Perhaps for dev-facing apps but such an interview process is overall misguided and immature.
we don't know the situation in this case.
I can think back to meetings where questions of similar nature have popped up. You have guys that want the precise numbers and refuse to make any assumption of any sort. You have guys that throw stupid guesses and just want to move forward. You have guys that do a little bit of thinking to come to a quick but critically thought out answer. This seems like a good way to identify which category you fall in and whether your approach is a good fit for the job.
I don't think it's a stupid or impossible question, but one that seeks to establish how you go about estimating tricky things and thus identifying fruitful territory for more rigorous research. Let's walk through it, with the awareness that we're trying to refine our techniques of estimation rather than caring about the actual number of barbers.
'Barber' implies haircuts for men. This is good, because the number of hairstylists that cater to women depends on fashion, which is hard to quantify. On the other hand, hair cutting is more related to hair growth. There's about 3/4 of a million people in San Francisco. Roughly half of them are men, so we have 375,000 potential customers. Most men wear their hair short, off the ears. Of course some wear their hair long and have it cut very infrequently, while others like it much shorter, eg with a buzz cut and have it cut more often...but some of them may cut their own hair, since a buzz-cut isn't too challenging. I'm going to assume the number of hippies cancels out the number of close-cutters because San Francisco has a bit of a hippy reputation. So much for hairstyling.
OK, so I've postulated 375,000 men who average out to a 'regular hairstyle'. And I've postulated that a regular hairstyle means not having your ears covered, ie the old 'short back and sides'. While it's growing, you could comb it out of the way or let it cover the tops of your ears, but once it gets half-way down then you're either growing it out or it's time to visit the barber. How much hair is that? My ears are about 2 inches high, but I have small ears. 3 inches sounds pretty big though...I'll guess the average is 2.5 inches, so half of that is 1.25 inches. That's already pretty fluffy though...let's round it down to 1 inch. OK, so 375,000 men get a haircut whenever their hair has grown by more than an inch.
How long does that take? Hair grows at about 4 inches a year, so let's say 3 months. Which gives us 1.5 million male haircuts a year for the whole city. (we could have started calling the population p and the rate of hair growth g[h] and so on, but why bother, it's a chain of reasoning we're concerned with here). A haircut takes, what, 20 minutes? it could be faster, then again some want a more difficult style. So let's guess that there's half a million hours of actual hair cutting (including the bit with the sheet and the sweeping up etc) going on in a year in SF.
Now we're getting somewhere. How much does a barber work? I'd say 45 hours a week. Some barbershops open early for the business crowd, but then they're closed on Saturdays. Monday-Saturday seems reasonable, as does 2 weeks' holiday. So one barber could spend a maximum of 2500 hours per year cutting hair. Only, that seems a bit high. Sometimes you wait in line, but I don't usually think of barbers as busy flat-out most of the time. 30 hours of cutting and 15 hours a week of of waiting for a customer seems more realistic. So 1500 hours of haircutting per barber (edit: 1650, but who cares). And dividing that into half a million hours of cuttable male hair per year gives me 333, the number of people needed to cut all that hair.
At this point you can start arguing about whether someone that caters to both men and women is truly a barber, or whether women can be said to be barbers even if they only cut men's hair. If your answers to those questions are no and no, and we go with the stereotype of a barber as a man who only cuts other men's hair, then I'd halve these numbers and guess that the number of 'pure' barbers in SF is 75-100.
OK, so this is 10 minutes of my life I won't get back, but if I was going to market something specific to barbers then I now have a decent guess at the number of potential customers in my local metro area.
Of course, you could have just said 'pass me a copy of the Yellow Pages and I'll tell you'. So having done the above, I went and looked that up and got 131 results at http://www.superpages.com/yellowpages/C-Barbers/S-CA/T-San+F... ...with 2 or 3 cutters at each shop, that would suggest somewhere in the 3-400 range, but some of these entries are for Salons and some are in Daly city or Sausalito, not quite in San Francisco. Still not definitive, but not too far off either. Sure, there's a lot of guessing and hand-waving here...but the important thing is that I arrived at an estimate that roughly correlates with reality. In this case I was able to check that reality (by looking up the number of self-identified barbering businesses) but once you become adept at this technique you can use it for anything, and then get on with solving the problem instead of feeling stuck by a lack of information.
Say, 375,000 men and 25% of them men get a hair cut every 2 weeks taking 30 min, most men get far fewer haircuts but they bring the average down to about once a month.
Av workweek = 40 hours * 4 weeks = 160 men per barber sounds low call it 200.
375,000 / 200 is less than 2,000.
A number out of your ass - regardless of how soundly backed with logic - is at the end of the day a number out of your ass. This isn't to say that all inference or estimation is bad - but rather that estimations done in a complete void of background data is practically useless.
A more concrete example: estimate the number of users our chief competitor has. I can go through this like a logic puzzle and come up with a number that has zero verifiability... or I can go look up relevant data (their page rank on Google, other available metrics on their site, etc) and arrive at a far better conclusion.
I agree with the GP that these exercises are pointless and unrelated to the job for which you are interviewing. As a traditionally educated engineer, my training teaches me not to guess whenever facts are available. Don't try to memorize and infer numbers - keep your references within reach at all times. An engineer who makes few assumptions about his data is one who makes fewer mistakes and costs less money in damage.
On the other hand, that's not always practical. Sometimes the facts aren't readily to hand or you have to make some decision that's time sensitive. For example, working in film production it's not so unusual to have to eyeball something and estimate your needs for time or material - you try to anticipate as much of that as possible in advance, but say you come to the set one day and the lead actor has fallen ill, so now you have to rearrange your shooting schedule on the fly...in which case it's not uncommon for a few key crew members to huddle, deliberate, and then split the difference rather than obsess over further optimization.
This isn't to say one should rely heavily on gut decisions, since that's likely to be self-defeating; on the other hand, you don't use a slide rule and protractor to drive.
Ah, but the most lucrative questions are about products not yet invented, for which there are few facts. They are lucrative because there is not yet any competition. If there were lots of facts available, ripe for the picking, then by definition the net margins would be terrible.
For instance, suppose you were a grad student at the MIT Media Lab in 1995. Does it make financial sense to join the work on an electronic ink product? The answer to that question could only have been derived from a series of guesses and wild deductions. You cannot just look up how efficient planar electroluminescent backlights are going to be in 10 years. Or how expensive and power-hungry non-volatile memory devices are going to be in 10 years.
For a research organization to invent and capture a new market, they have to be good at making and using wild guesses about the future. (Looking up answers is valuable too, but for different reasons.)
How efficient will planar electroluminescent backlights be in 10 years? That's a good question - and one we can make an educated stab at given the right historical data, the right experience in forecasting, and a little bit of plain luck. Heck, you're now talking about an entire field of mathematics and engineering in and of itself!
Compare this to the Google interview though - where they expect you to pull a number out of your ass, with no opportunity to consult historical data, no field experts to interview... no due diligence done at all. It is either an extremely poor approximation of real-life problem solving skills, or everyone at Google is recklessly cowboy and trying to deduce every decision ever by sheer will of logic alone.
The best answer would be, there are 14 haircutting places within the shopping disctructs of the U of C, and it is currently overzoned for hair currently, accroding to the maroon. Only two are true barbershops. It consists of three long blocks. Lets take the U of C landscape to be somewhat abnormal, and that there should really only be 7, of which 1 is a barbershop. There are about 24 neighborhoods in chicago. There should be 24 barbershops...ect ect....
Just for the record...
As your interviewer said, these questions are asked just to see how you will come up with an answer. The actual number hardly matters, so long as you can sell it to the interviewer. Pushing you is part of the process, as well, to see how you hold up "under pressure."
If you want to be uncharitable, this is much like what a management consultant does -- come in, get some problem from a troubled company ("How can we improve sales by 20% in six months?"), develop a strategy, and then convince the client that they should do it. The interview technique makes sense for that context because it selects for people who can pull this off.
Actually, for a PR role I don't think this question is such a bad fit. You will have to think quickly on your feet, answer hostile people, and come up with diplomatic, plausible answers to crazy questions ("why does your product not work with Slackware?"). The precise answer is of course important, since if you're wrong you will be caught, but how you react is more important.
These 'stupid impossible questions' have a long history. http://en.wikipedia.org/wiki/Fermi_problem
(Barbers cut the hair of half the population (the male half) around every two months. The population of San Francisco is about 750k. A haircut takes about 30 minutes, and about 50% of the time a barber is cutting hair. This gives about 8 cuts per day, or about 60x8 = 480 haircuts per every two months. So to service 750k/2 of the population you need about 750k / (2 x 480)) = about 781 barbers. Or roughly one out of a thousand people is a barber.)
“That’s all. Good luck with your job search.” The phone clicked-- I was stunned.
When I was 'senior' I never applied to McKinsey, because I'd heard so many horror stories about their interviews - I just didn't want to go anywhere near them. I landed a job with one of their main competitors and spent 5 happy years there...
Is SPEED of critical thinking important? How many positions at Google require people to think on their feet? How many positions require them to be comfortable/effective talking to strangers on the phone (for this woman's position, it might be the case)?
Check out the War For Talent ( https://www.amazon.com/dp/157851459 )... Andrew Chen has a good blog post talking about it: http://andrewchenblog.com/2009/07/28/what-if-interviews-poor...
Bottom line is that studies show over and over that "if you look at the marks that people get coming out of a hiring process versus the on-the-job marks they get in their first year in a job, they are actually not correlated at all."
"Our interviews are more to do with practical problem solving, not with puzzles and tricks. Our interview scores actually correlate very well with on-the-job performance: we are doing quite well at hiring the right people, we believe, and we work hard at analyzing the process. Peter Seibel asked me if there was anything counterintuitive about the process and I said that people who got one low score but were hired anyway did well on-the-job. To me, that means the interview process is doing very well, not that it is broken. It means that we don't let one bad interview blackball a candidate. We'll keep interviewing, keep hiring, and keep analyzing the results to improve the process." http://www.mv-voice.com/square/index.php?i=3&d=&t=16...
I could count the number of people who passed one of my phone screens on one hand (and I considered myself a fairly easy interviewer).
Part of my decision to drop out of the job market and focus full-time on my company (to pretty reasonable success this year) is because I like being paid based on a judgement of my work/products, rather than some half-assed assessment of me as a person made in an interview.
Any judgement made in a 45-minute (or less!) interview is going to be half-assed. That's the unfortunate way of the world. How do you think people should interview?
(Genuinely curious; I do interviews, and I think I do pretty well, but it's difficult to honestly examine one's own methods without feedback.)
If you have to interview strangers, I think it's good to inquire into their technical background until you have ample confidence in their technical abilities, and take the rest of the time to discuss career and company goals, personalities, hobbies, etc., in a lax and non-rushed manner. I'd invite the candidate back for a follow-up interview and talk more and then invite him to work out of your office for a few days (with pay, of course).
I think it's much better to have a relaxed and friendly decorum and perform a series of informal "interviews" because you'll learn a lot more about the candidate if he feels confident and open than if he's rushed to answer a bunch of silly logic puzzles and give diatribes on his five-year life plan.
It is possible that this person is being interviewed by Google as a result of a referral by another employee within the Google, or even a referral from the hiring manager themselves.
Unless what you mean is that a hiring manager only consider people whom he and every other potential interviewer already know before the interview process even begins. The odds of ending up with such an arrangement at a place the size of Google, or even a place 1/100th the size of Google, seem insanely remote.
Someone on an interview loop at a large organization is bound to not know you from every other candidate who walks in the door. Even with phone interviews, odds are they call people based on factors entirely other than "do they know this person?" The best he may know about you is that some other person in the organization referred you, but it is not obvious whether they'll appreciate knowing this or be pissed off that their objectivity is now screwed. Some interviewers really prize trying to be as objective as possible in interviews, because interviews have a habit of being horribly imprecise anyway. But then, so do referral from J. Random Employee ("I have this cousin who's really good with computers; he helped me setup Outlook and everything. We should hire him a as software engineer.")
But then, maybe that is your point. If a company ends up at a size where they can't rely on connections, they're too big already.
Would he be happy programming in Java?
Each time they said "this interview will take about 30 minutes," but each one ended up being around 1.5 hours.
It was grueling, but fun. I'm not sure what happened because I didn't hear back after the 3rd interview. It was at least a nice feeling to know that all of my classes in school had helped me with the answers.
The problem only sounded easy? Isn't this what you learn in 3rd grade? When you can't do this stuff you shouldn't be allowed near numbers.
Personally, I solved it easily in my head. But, I had to read the problem the first time, then read it again slowly getting all the numbers into the proper places in my head. An interview is a stressful place, so easy things can get a lot harder.
That's why the true test of a hiring process is the firing process.
If you can get rid of people that can't hack it, rather than letting them gather as detritus in your system, you'll be far better off than if you simply pretend that you can actually avoid mistakes.
When the cost of a false positive is high, e.g. a bad employee can be very expensive in terms of time and money before he is identified and fired if he is fired at all, then it is worth the cost of a few more false negatives to be more sure that you aren't getting false positives.
It seems that very often someone who is the victim of being a false negative will rail against the system and claim it is unfair. If you can get them to look at it from the other side they will often agree the practice is quite reasonable.
You work for a digital age media company who has already achieved superior market dominance in an industry rife with failure and turnover. Your company's stock, though depressed, still sells for multiples above its competition and the option pool is pretty full and limited.
The company's single main product continues to grow its revenues nicely but has failed at virtually all attempts to broaden its product line so it remains reliant on its single huge product which may come under government anti-trust action at some point in the future to say nothing of two leading competitors aiming to unseat it. It's only other breakthrough products are given away free or at nominal charge with no discernable profitable business model.
Is it a good career choice to join or stay with this firm even though they pride themselves on asking stupid quiz questions to gauge your intelligence and make you feel very special if you are offered a position?
Why are people so upset about the "quiz questions"? Is it unreasonable for an employer to expect you to think? (Is the "right answer" ever the goal of these questions?)
First thing I discovered though from helping other people on other sorts of collaborative projects on the web:
Get paper for this stuff if you are out of practice, and ask to wait for an aswer while you write it down, and if you forget something, as to repeat. Always good to write somehting down- shows you are listening. She didn't.
Be a little more wild with your answer. Not over the top. But just a little. I got that last night from someone at McKinsey. Was talkign to a class of mine about the history of business. Someone asked. Don't be too much though.
And reach out about your humanness. Not everyone is perfect. If your weak point is Back of the envelope stuff, then it is your weak point.
Speaking of which, since I am taking my time (becuase I can't freak out any more, I just can't) How do I brush up on those questions? And that way of thinking. I'm good on the creative side with large data sets and how to sort out problems, but not on the calculations side...which sucks.
I realize I can do a lot of things with time and effort. I feel pressure on the time part, Overloaded. I'm doing a bit too much on top of that. I'm a little less that one week to my bachelor's critique in new media/internet art. We're a crazy bunch of folk, them artists. Long term I want to switch to learning coding, and haven't had the time to sit down and even think yet...
Or really apply for jobs yet. That's uhhh after next week, after I finish classes. When I know where I'm living/doing. That's normal for a college student though where I am...jumpy folk, mostly halfway through a very short midterm cycle...BA nearly got deleted, those sorts of things. still coming off of that sort of thing.
I know Google is a big company and all (sampling space fail) but that really turned me off.
But that is a useful skill, particularly in conjunction with a problem-solving attitude which they repeatedly emphasized us to do.
And the book Innumeracy by Paulos gives examples of good problems to check with: "Is there a cubic mile of human blood in the world" and "How long would it take to move Mount Fuji" as a couple of examples.
It doesn't sound like a good sign if your latest math was as a freshman if you are looking for a software career.
One question (paraphrased): $0.10 cpc, with a 20% of visits resulting in a click. How many visits needed to make $20?
After five painful minutes the annoyed interviewer gave me the answer...She made it sound so easy; I felt like a moron.
She is innumerate.
If I were illiterate, I'd probably describe an interview at McGraw Hill as nightmarish. "After five painful minutes of trying to sound out the words the annoyed interviewer read the sentence to me...She made it sound so easy; I felt like a moron."
The girl goes to Syracuse, which is a somewhat selective University. She would not have gotten in if she couldn't do the math (her SAT scores simply wouldn't be high enough.)
This question would have been easy for me and actually would have probably boosted my confidence during the interview. But that's because I'm a quantitative person. Throw a question I was completely unexpecting though and I could be stuttering and saying stupid things. I'm sure there would be some questions or exercises the author could complete far more smoothly than I could.
Calling her innumerate (and making the analogy of her being illiterate and thus incompetent) for this slip makes me think you haven't been on many interviews yet.
Google's interview process isn't a nightmare. It's entirely typical. If you plan on interviewing for any job, you should spend a lot of time studying the interview process and how to excel in it. If you're interviewing for programming jobs, this course is an invaluable resource: http://courses.csail.mit.edu/iap/interview/
Read all the handouts 5 times, and you won't be caught off guard like this girl was.
http://courses.csail.mit.edu/iap/interview/Hacking_a_Google_...
http://courses.csail.mit.edu/iap/interview/Hacking_a_Google_...
http://courses.csail.mit.edu/iap/interview/Hacking_a_Google_...
http://courses.csail.mit.edu/iap/interview/Hacking_a_Google_...
http://courses.csail.mit.edu/iap/interview/Hacking_a_Google_...
FWIW, they did ask me for a lot of awfully detailed information about my current and past compensation packages and what other companies I was interviewing with. I mostly declined to provide that information, and they didn't push it.
Back when I was in my final year of uni I interviewed for a set of blue-chip graduate recruiters who threw similar questions at me. I distinctly remember sitting in a Data Connection office somewhere trying to work out how many petrol stations were in the UK. I was terrible. But there are ways to get better at this and it's really no secret that Google asks these kinds of questions. I think they reveal two things about the candidate - how good they are instinctively, and how well they prepare.
Obviously Google asks candidates who get past a certain point to sign a NDA, but there's still a surprising amount of information out there. I was recently helping a friend (and have previously helped an ex) with interviews and preparing for the logic and theoretical comp.sci. parts was actually quite a lot of fun. Maybe because I didn't have the pressure!
The engineer says that he got lost when she mentions ads might have a 25% click through rate but in another question the click through rate was 20%, as an example. She probably thought, but did not write that her earlier estimate would have been ok or acceptable which would be confusing given the engineer's reaction.
Also, if said question was meant to test reasoning skills and not a raw answer, then a wrong estimate for click through shouldn't "lose" anyone. After all, if you haven't worked in search or heard of google or the internet ad business internals, how would you know what the click through rate should be more like? Advertising is but one of many industries.
I think google needs to be a bit more careful about how they ask questions or at least have interviewers talk to each other. Probably too difficult since they all have other tasks and duties to do.
chicken/egg... how are you going to know that without talking to them?
However, to that end, could you just raise the bar on the resumes and also the subequent first-round phone screens to reduce the number of 2nd-, 3rd-round interviews? The Google application (for non-college recruits) is already extensive and probably acts as a weed-out mechanism for many people deciding to just apply on a whim.
Sure, a good GPA is good. But if you back it up with experience, you are ahead.
I quite enjoyed the back of the envelope calculations during the early calls, as well as talking about interesting products I had encountered recently.
It got quite interesting on-site. I really enjoyed the first couple of days of interviews, which focused on design ("design a shopping mall"). The last day was still fun, but less enjoyable, as it involved coding on a whiteboard, estimating the computational complexity, and then improving its efficiency. Then I was asked to spec out the requirements for adding unit tests to a programming language.
I felt the interviews were fair and well-balanced, the main sticking point for me was the emphasis on GPA and academic history.
Question: is it more important to keep out the bad ones but lose some good ones, or vice versa? (ie, what's the correct balance between false positives and false negatives?)
I conjecture that what we are discussing is primate social behavior (yes, "monkeys in a tree") and social hierarchy in action. Of course we _are_ primates, so maybe it _is_ vital that Google hire enough "alpha males" or whatever.
I wouldn't work for a company that rate a person by quizzes or tricky questions.
If she thought about her own usage, she'd realize that it was an insanely high number (had she ever clicked on a single gmail ad, let alone 25% of them?).
It's dangerous to generalize from yourself like that.
“Google places four ads per e-mail opened in Gmail. Advertisers get to pick their click-through rates, which can be as little as $0.05...Say each G-mail user opens seven new e-mails a day. They would see 28 ads. If they click on ¼ of those ads, then only seven ads are clicked."
Gmail probably has something like 150 million users, so her figure of 7 ads clicked per user at a minimum of 5 cents a click would result in 52.5 million dollars a day. At some point she should have realized the void between her new analysis and her original $70,000 guess. The whole point of the question is to examine your analytical and estimation skills. The fact that she didn't notice that she was moving towards and answer 750 times the size of the her last one says a lot.
But overall, it was probably a good thing for her not to go there. Sounds like Google has a particular mindset (one that reminds me, anecdotally, of stories of Microsoft 15-20 years ago), and she wouldn't fit there. I'm not at all convinced that means she couldn't be effective at marketing somewhere else, though.
For my own part, never having bought Google ads, nor having displayed them, I would rather estimate no more than 1% of people would click on them no more than once per day. That's probably because I'm cynical about ads, use AdBlock, would rather rely on search and recommendation for finding products, and so do my peers. I don't have a good pool of knowledge for answering this question in a way that would be accurate, no matter what my estimation skills are.
Then again you could figure Google makes about $5 billion a year in profit, say a tenth of that comes from gmail, and the profit margin is 10%, suggesting ~$15m a day in earnings (not profits) which is off by a factor of 500 from the above. That sounds a lot more likely.
"In the second quarter alone, Google has managed to reel almost $1.5 billion in earnings."
"If you do the mathematics here, Google is making upwards of $4 million daily"
Except they mistakenly used the quarterly earnings in place of annual earnings. So it would be in the range of 4x that.
Yes, indeed. Someone who has a slightest clue about the whole stuff just can't say 1/4 of users will click an ad in Gmail. I am sorry for her, but that is just so off...
That's even worse: she assumed that 4 ads would be presented per e-mail, so the CTR would be 100% per e-mail.
That's beyond absurd.
First easy thing to do which isn't describe. Tell the person to sit down with a pen and paper. And then talk about the why and how. That was the demeaning part. Antoi-collaborative, very scary.
Even at Google, a job is not a vacation. Wanting to hire people who react well under pressure is completely valid.
The mistake, which is not at all unique to Google, is to think that "high pressure interrogation at a job interview" is usefully similar to the kind of pressure that might occur on the job. For some jobs it will be. For many others, it's completely different.
Compare these scenarios: "QA just found a huge, unexpected performance problem in this server application and no one knows what's causing it. The application goes live in 48 hours and you and your team have until then to make it handle ten thousand times as many users as it does now." vs. "You just landed after a 10-hour flight and will be meeting a major potential customer in 30 minutes. TSA blew up your laptop because it looked suspicious and the airline sent your luggage to Albuquerque so instead of a carefully-prepared presentation all you have are a couple index cards with vague notes about the product. If you don't make a sale, your company will be bankrupt in a week."
Google is not going to be bankrupt in a week. If your interviewer is really smart, do the Seth Godin thing: freelance the person for a few weeks, or offer them a real life case they are currently working on to see what that person is actually going to do.
One of the ways I figured out I would make a horrible teacher was I worked as a teacher. I really believed and worked very hard as a teacher. Ultimately, I needed a more collaborative environment, and I was stressed out because I met some really smart kids who were flunking half of exams on purpose when I confronted them about it. They would not work with me to fix these skills in third grade, particularly when there were background issues going on, and I was not the primary teacher. I found it not appropriate for me. I found that really high pressure, and not appropriate for me. Meanwhile, I know I will stay up all night on my own unpaid looking for affordance of different websites and how they can be applied for different business reasons. There you go? That seems to be appropriate for me. I just wish I knew more people in that field, and I wish I had the time to learn to code (after first round BA critiques....)
Interviewers need to sit down and know what is the pressures of the job, Half that interview would not have helped her at all. Furthermore, It is can I work with that person on the job, and help me and her reach a goal under pressure. That's a reasonable expectation. Very reasonable.
The second point of your comment is legit - this sort of time/pressure constraint isn't really representative of the workplace as a whole. Nobody should have someone hanging over them making sure you do your math right in under one minute - you certainly don't at Google. The interviewer probably should've tried to make the candidate feel a bit more at-ease.
But the sort of quick estimation skill necessary for these interview questions is really important. There've been countless meetings when someone (often me) has proposed a solution and I've done some quick mental math calculations only to find out that it just won't work. It's really valuable to get those calculations done in a minute so that you can brainstorm new ideas, rather than waiting until after the meeting when you probably just won't do the math at all.
And this is something that I really wish schools taught more of. Being able to get a quick, mostly-right-but-slightly-wrong answer, and being able to tell what ways your answer is wrong, is probably more important than being able to come up with exact answers or parrot back the formulas you supposedly memorize.
I would want to work out that problem with someone. For that math problem right:
lets ignore the 20 people problem (aka 20%) right now and pretend that all the people who visisted clicked. for every 100 people who visit, they now get 1 dollar (it was ten cents) before). in order to get $20 if a hundred people visited for every dollar, you would need
20,000 people.
One problem, they need to click. and only 20 people click per 100 people. so in order to really make that money, you would have to multiply again by 20. I would take the 2s out and start counting 0s because I would get confused at this point.
400,000 people. I think. I may have screwed up the 0s. But If I didn't have a chance to slow down and write down the problem I think I would have screwed that up badly. I'm not sitting around and doing those math problems all the time...
If I was at a job interview and was asked these sort of puzzles, I wouldn't feel under pressure. Instead I'd think "Cool, I like solving puzzles! And I'm good at it too so this is a chance to make a good impression." Maybe Google are looking for potential employees with that attitude?