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Why would I move Mount Fuji

No.... Really...

Okay, not really.

www.marktaw.com
Monday, May 05, 2003

The interviewer asked: "How many ping pong balls would fit in a 747?"

"Oh, is your organization struggling with this particular problem?" I asked back.

R. C.
Monday, May 05, 2003

Is it a freighter 747 or a passenger configuration? :-)

Patrik
Monday, May 05, 2003

I get questions like this all the time - from clients and managers. It's always important to gently ask them why exactly they would like to move Mt Fuji or to put ping pong balls into a 747. More often than not, they want a particular feature and are telling me how to implement the feature at a code level. Of course they only have a limited understand of how the software works, but they're in charge and they know best - not these code monkeys.

If you can extract what their actual requirements are, then you can usually avoid having to move Mt Fuji.

I'm not going to get the job am I?

RB
Monday, May 05, 2003

Oh, yeah, another really idiotic "MS puzzle" allegedly used for MS for their interviews.

Basic mathematics can help you estimate that. I would also press the ping-pong balls together, in order to make them compact and fit more in that airplane, and make calculation easier. :)

My question is: what does this "puzzle" test?

The capability of roughly estimating something?

The capability of making a wild guess?

The capability of instantly bullshitting the interviewer?

When interviewing programmers, let them solve a HARD problem, in code.

One that takes a few hours, and requires brains and (if possible) the specific programming knowledge you need them to have.

This is testing them by giving them what they will actually do on the job.

Michael K.
Monday, May 05, 2003

In order to transport as many ping-pong balls as possible using an airliner, I would put in a ping-pong balls making machine (they are rather small), and the materials needed to make the ping-pong balls.

But the question is still very irrelevant for software developers.

Michael K.
Monday, May 05, 2003

"How many ping pong balls would fit in a 747?"

All of them, one at a time

Danil
Monday, May 05, 2003

[[ But the question is still very irrelevant for software developers ]]

Well, I think *it might be* relevant for software developers by testing one's creativity. But I would say there are many other *much more* relevant things to see so that spending time on those MS-like puzzles seems just a waste of time to me.

Evgeny Goldin
Monday, May 05, 2003

["How many ping pong balls would fit in a 747?"]

I would suggest 348, one of them per seat. Get a good ROI from those golf balls ;-)

Ian Stallings
Monday, May 05, 2003

I agree that extracting what it is someone really wants to do is the best way to go about this kind of thing. Sometimes, though, it's like pulling teeth.

Their assumptions are so deep rooted they're impossible to get at.

They're just passing along orders from above and don't really know why themselves.

The real reason is to make themselves look like they're accomplishing something this quarter.

www.marktaw.com
Monday, May 05, 2003

I think that those interviewers who ask this type of question (excluding those who are simply asking it because they heard it is a Microsoft-style question) generally want to see how the interviewee will tackle the problem.  The refinement of the the requirements can parallel the development of specs for a software project. 

Take for example the aforementioned 747/ping pong ball question.  Those who do well will not be those who hunker down and try to work out some formula for 747/ball volume (although some interviewers may want this) but rather use the question as an example of their ability to refine an open-ended requirements statement.

- Are we talking about a working 747 or simply the shell (can I fill the wings/engines/shells/etc)

- Will the balls need to be usable post experimnent (can the balls be flattened/melted/etc)

- Is there any other activity (ie a game of ping pong) that will need take place

- Are there any time restrictions

- Will the ping pong balls be in any sort of containers or packaging

DW
Monday, May 05, 2003

> Those who do well will not be those who hunker down
> and try to work out some formula for 747/ball
> volume (although some interviewers may want
> this) but rather use the question as an example of
> their ability to refine an open-ended requirements
> statement."

DW - Close. You're still refining an already laundry-list like requirement.

A better question is "Describe to me your desired end-state and how does that differ from the current situation?"

That'll get you and the person giving the requirements on the same page - now you know their goals and you know their reasons.

From there you can refine the requirements more. "Why are you choosing to do this via a 747? Why not do it via trucks?" "What are my constraints for working with the 747?"

If someone were really transporting ping pong balls, they'd put them in crates and on pallettes. Another constraint is the cargo hold - is it pressurized? If not the ping pong balls may explode due to the difference in air pressure.

www.marktaw.com
Monday, May 05, 2003

"348"

Ian,

ROTFL!

Dennis Atkins
Monday, May 05, 2003

Since the thread's been jacked by the 747/ping pong ball thing, here's a link to a fun site where some guy tries to answer the question "How much is inside?" using hands on tests.

http://www.cockeyed.com/inside/howmuchinside.html

One of the questions he tries to address is how many ping poing balls fit in a chevy trailblazer.

Bill Tomlinson
Monday, May 05, 2003

That guy definately gets the job.

Roger Fong is out of the running for cheating.

www.marktaw.com
Monday, May 05, 2003

LOL! I wonder how the interviewer would react to an Ian style answer:
"How many ping pong balls would fit in a 747?"
"Twelve"
"TWELVE?!?"
"Are you trying to say you don't think twelve ping pong balls would fit on a 747? I'm pretty sure they would..."

Philo

Philo
Monday, May 05, 2003

Talk about missing the point.

The reason these questions are asked is NOT to get an approximation of the correct answer. It's to see the thinking process that gets to the (for sure incorrect) answer that the applicant gives. This should be made clear 1) at the beginning of the interview; 2) when this question is asked.

If I were to ask how many ping pong balls fit into a 747, and the guy answered "42", without missing a step, that's a no-hire.

However, if the applicant were to estimate that there was a 32% decrease in volume because of the negative space outside the ball, and that one ball was about an inch in diameter, and that one seat area could hold 3ftx3ftx7ft worth of balls, plus the aisle, etc., etc., that's a pretty good indicator of how this person thinks.

The answer is totally irrelevant.

Tim Sullivan
Monday, May 05, 2003

new math...

Nat Ersoz
Monday, May 05, 2003

Rather than starting a new thread, some one a couple of posts up got me thinking...

"Why would I want to know how someone would move Mount Fuji?"

What thought processes am I looking for when I ask that kind of question?

www.marktaw.com
Tuesday, May 06, 2003

"If I were to ask how many ping pong balls fit into a 747, and the guy answered "42", without missing a step, that's a no-hire"

and *thats* an arbitary, random decision.

A chap who answered that is providing an arbitarily random answer to an arbitarily random question.
To me thats a perfectly reasonable response :)
He has, in fact, recognised the arbitary nature of the problem in an instant and provided an arbitary answer.

I once had a client ask whether I used the 'internet protocol' in the solution I provided him with.
my answer?  'yes'

But on another day I might well have answered 'no', the question was irrelevant and represented the clients need to appear knowledgable rather than his need for knowledge.
a *good* developer should be able to recognise unimportant questions from important questions, useful data from non-useful, good code from bad code and good design from bad design.
IMO a programmer whose first instinct is to take a question like the above seriously is one who is 6 iq points short of that which will be required.
<g> OTOH a programmer who recognises the pointlessness of the question, points that out loudly and moves on, but nonetheless finds himself unable to resist trying to solve it in his head at 11pm at night when he  needs to be up early the next day is guaranteed a job with me...

networking guru and gungho programmer
Tuesday, May 06, 2003


You wouldn't hire a guy that responded with the answer to life, the universe and everything?  Somewhat narrow thinking...

Joe AA
Tuesday, May 06, 2003

So what you are saying is that the ultimate question is "How many ping pong balls..."?


Tuesday, May 06, 2003

Networking guru - I agree with you from the technical/geek point of view, but you're missing the point from the software developer/architect point of view.

Interviewer asks silly question.
What is you objective here? Ostensibly, since you're spending valuable time talking to the asker of the silly question, you are here to get a job.

So, within the boundaries of the problem at hand ("get a job"), it is not a silly question. It is a question that was asked for a reason. Since it's doubtful that the company you're applying to has a current business problem depending on the relative volumes of ping pong balls and passenger aircraft, then the goal of the question is most likely to judge your approach.

Therefore, a measured, logical approach is called for, while thinking out loud to make silly question asking person happy.

If you want to go with "I might as well say 'forty two,' since that is a stupid question" then one would have to wonder why you're there in the first place, since your goal does not seem to be "get a job"

Philo

Philo
Tuesday, May 06, 2003

If my goal is to 'get a job' with an organization for which I would actually like to work then 'forty-two' may indeed be the correct answer.

If my goal is just to 'get a job' any job then it probably isn't.

Stephen Martin
Tuesday, May 06, 2003

Hi Philo,

<g> that is *exactly* where my logic falls down of course...

I really should have added to my previous comment the fact that any programmer who doesn't realise that his/her main priority when Im interviewing them for a job is to clean my ass with their tongue is prolly not bright enough to cope well with the more advanced areas of computer programming...

networking guru and gungho programmer
Wednesday, May 07, 2003

How much money do I have in my pocket right now, and come up with an answer that you are 95% sure is right.

Has to be one of the worst of these type of questions I was ever asked.  The guy was nasty about it, too.  That didn't help.  I still got the job.

gerry_the_germ
Thursday, May 22, 2003

what does Ping Pong Ball and 747's have to do with the pice of rice in china?  hehe.

ewfnj
Monday, December 22, 2003

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