Interview “Stumper” Question: Part 1

It’s been an awfully long time, I’m afraid, since I’ve heard of a company that was using a truly inspired or innovative approach to the interviewing process.  It seems that the majority of companies today continue to fall back on the litany of shopworn interviewing questions that one can find in any “What Color is your Parachute” or “Knock ‘Em Dead” type of book.  You know, the greatest weakness, proudest achievement, what would your last boss say about you kind of stuff.

Then you’ve got the employers on the other end of the spectrum, who pride themselves on ambushing applicants with “stress” or “puzzle” questions in order to test a person’s brain power and/or ability to think quickly on their feet.  Microsoft is perhaps the most famous company in this niche, inspiring an entire book (How Would You Move Mount Fuji?) devoted to teaching people how to anticipate and respond successfully to these kinds of out-of-left-field inquiries.

And then there’s just plain crazy.  There’s one company in town (I’ll withhold the name, just to be safe, but it’s not likely a firm you’ve heard of before) that takes interviewing to the level of “performance art” by having the interviewer pretend to be drunk on a bottle of tequila and then get into a fistfight (or close to it) with another office mate.  I’m not sure what quality or competency they could possibly purport to be testing in this scenario, exactly, but that’s how they go about it.  I also happen to know that this same company cheerfully invites vendors to come in and pitch their wares to them — just as long as it’s at 3:30am on a Saturday morning, to make sure the vendor knows their place and REALLY wants the business!  My last employer was one of the firms that was asked to do this, in fact, and they sucked up their pride and went on this ridiculously early appointment, just out of sheer curiosity.

At any rate, back to those “puzzle” interview questions for a moment.  While such lines of inquiry are usually directed at computer programmers and engineers, I actually know a marketing professional who said she was subjected to this kind of brain-teaser question in a recent interview, right out of the blue.  Here’s what they threw at her:

The “Drunken Mice” Interview Question

Let’s say you’re given 16 bottles of wine and must drink one of the bottles 24 hours from now, but unfortunately, are also informed that one of the bottles is poisoned.  The only tool you have at your disposal to test the bottles is four mice.  It takes 24 hours for the poison in question to kill mice.  How would you use the mice to test the wine and prevent yourself from drinking the poisoned bottle?

I’ll post the answer early next week — as well as the two actual answers my acquaintance tried giving, simply by thinking on her feet.  If any of you are “puzzle freaks” and want to try to guess the solution in the next 72 hours or so, however, feel free to give it your best shot and submit a comment!


13 Responses to “Interview “Stumper” Question: Part 1”

  1. The “find one unpoisoned bottle” is such an elegantly simple solution to the problem, rather than finding the poisoned one… But it’s an easy trap to fall into – I do it all the time. It’s like the poison bottle is practically jumping up and down, waving it’s arms, screaming “hey! Look for me!”

    What it comes down to is clarifying, in absolute terms, exactly what the objective is before undertaking the task (my recent PM credentials showing up here…)

    Which is a REALLY good exercise to undertake before walking into an interview.

    Could the garden variety objective of “to be offered a job” be considered similar to “find the poisened bottle”?

  2. The most comprehensive and very well thought out write up I have found on this subject on the internet. Keep on writing, I will keep on coming by to read your new content. This is my fourth time stopping by your Blog .

  3. Leslie: Good point. If the goal is to find ONE SAFE BOTTLE versus to uncover the ACTUAL POISONED BOTTLE, your logic certainly makes sense, to me. I guess it all depends on how exactly the question is phrased by the interviewer. In most cases, after looking at a number of examples on Google of where this question was asked, I think they do ask you to determine which one is the poisoned bottle. But you’re right, the way I posed the question in my first blog entry left it open to your interpretation — and your much easier solution. Good catch! 🙂

  4. Don’t you just have to know one bottle is safe? I’d just give wine from one bottle to each of four mice. Wouldn’t any mouse still alive in 24 hours would have drunk from an unpoisoned bottle? If one mouse dies, don’t drink from that one.

  5. Dean: Good thought, but where I think that strategy breaks down is the explanation, in the puzzle instructions, that it takes 24 hours for the poison to affect the mice. So you’d only have the time to test one bottle before the time period elapsed and you have to pick a bottle to drink…

  6. At the risk of over-simplifying and missing something here, why not just have the mice sample one bottle. If they die, it’s poison, so pick any other bottle and drink it. If they live, the bottle is safe, so drink it…..

  7. I get stumped because I know that it is impossible to feed 4 mice from 16 bottles of wine in zero minutes. I also know that no poison works exactly to the second. Hence, say it takes even 30 minutes to dose the mice (I actually did critter experiments back in the U of T day). The results don’t come in until 24 1/2 hours after the start, and you were supposed to drink your sample 1/2 an hour ago. so you have a 1 in 16 chance of being dead. Which is exactly the same probability you had to begin with. If you were willing to die for this job, any bottle will do!

    you don’t even get browny points for stating your assumptions in these problems, or asking clarifying questions because it is highly unlikely that the interviewer even understands the assumptions their ideal answer involves and doesn’t know the field enough to clarify assumptions, and then they think that you “ask too many questions”.

    sorry, didn’t mean to whine

  8. Matt
    You are not exxagerating when you say candidates are
    asked to jump through hoops. I have been an acct
    for 36 years. You don’t say to your mechanic “gee,you
    have too much experience” or your doctor or lawyer or
    indian chief. It really makes almost no sense. What
    does make sense is the excellent advice you give on the
    subject. There is no rhyme or reason. You have to
    stay the course and try to keep your sanity.

  9. I can’t pass up a good puzzle.

    Ok, here goes. I’m assuming that the poison, no matter how dilute, will kill in 24 hours. And assuming all the mice are in reasonably good health…

    Take the first bottle and set it aside. Take 4 little mouse sized wine glasses and mix wine from bottles 2,4,6,8,10,12,14 and 16 in the first glass and feed to mouse #1. Take wine from 3,4,7,8,11,12,15 and 16 and feed to mouse #2. Take wine from 5,6,7,8 13,14,15 and 16 and feed that to mouse #3. Take wine from bottles 9-16 and feed to mouse #4.

    If the poison is in bottle 1, no mice die.
    If in bottle 2, only mouse 1 dies.
    If in bottle 3, only mouse 2 dies.
    If in bottle 4, mice 1 and 2 die.

    If in bottle 16, all the mice die.

    The pattern of mouse demise will tell you which bottle contains the poison.

  10. Being no math wiz…but…..divide the bottles into groups of four and assign one group to each mouse and give them samples from their group. One (or more)mice will die from one of the bottles in their group, therefore making the bottles in the other groups safe to drink from (unless all mice die….)

  11. Wow, Matt. All I can say is thank goodness I work for myself! Aside from the fact that after working for myself for nearly 20 years I am absolutely unemployable, I would be fully compelled to walk out of an interview where they displayed such arrogance and disdain for the people who are applying for a position.

    Can you imagine what keeping a job with a company would be like if getting a job with them is like this?

    I would wonder what the turnover rate is for companies that engage in those kind of practices.

    Thank you for always shining the light on the weird and wonderful!

  12. I went on an interview last friday….went back
    tuesday and was told “we are 98% there go tell your
    wife to relax” and that is where we left it. Feels
    like I am left hanging on a cliff and waiting to hear.
    Employers, who have the upper hand, have left common
    sense in the dust. Another employer a few weeks ago
    gave a 2 1/2 hour 3 part test right before the
    interview. Absolutely no common sense.
    Really could use a dose of sanity.
    Companies are off the wall these days….


  1. david - September 28, 2011

    my site…

    […]Interview “Stumper” Question: Part 1 « Career Horizons: The Blog![…]…

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