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Home -> Community -> Usenet -> c.d.o.server -> Re: Interview Question (with Shannon twist)
In article <33ced3e3.0_at_lightning.ica.net>, dane_at_ica.net (Dan) wrote:
>In article <5o6koi$r1s_at_mgh_cs1.mgh.com>,
> r#as#crystal_at_d#as#ri.mc#as#graw-hill.com (Rona Crystal) writes:
>>In article <FscdMLASQZozEwmG_at_jbdr.demon.co.uk>, Jeremy_at_jbdr.demon.co.uk
>>says...
>>>
>>>In article <33A06770.161E_at_aig.vialink.com>, Johnny Barnes
>>><jbarnes_at_aig.vialink.com> writes
>>>>Last summer I interviewed with a large airline firm for a dba position
>>>>and the first technical question asked was - If you have 8 marbles all
>>>>of the same size but one is heavier how can you find the heavy marble
>>>>with a set of balance scales in just 2 weighings?
>>>
>>>Well clearly you'd need 3, so I guess this must be a lateral thinking
>>>test - probably involving some highly debatable "trick".
>>>
>>>What was the answer and did you get it correct?
>>>
>>>--
>>>Jeremy Rickard
>>
>>
>>No trick here, just have to look beyond the obvious, but I'm not sure that I
>>could have come up with the answer under pressure of an interview.
>>
>>Divide the marbles into three groups of 3, 3, and 2. Put both groups of 3
>>on the scale (weighing #1). If they balance the heavy one is in the 2 group
>>and you put each of those on the scale (weighing #2) and you have found it.
>> If the two groups (in weighing #1) of 3 do not balance, you know with group
>>has the heavy one so weigh (alternate weighing #2) any two of them and you
>>now know which one of them it is.
>>
>>While skills like this may come in handy in identifying and solving
>>problems, I'm not sure the lack of the correct answer is meaningful. The
>>first time I read the question in the original post, I thought about it but
>>couldn't get the answer. When I saw it repeated in this post, the answer
>>just popped into my mind. So, so I guess that I would have missed it on the
>>interview.
>
>
>I have an extension to this question.
>If the guy answered correct to the first question, you can ask him quick:
>
>"What is the amount of information extracted from this experiment
>in Shannon(*) sense ?"
>
>If he doesn't choke and tries to mention some logarithms of probabilities then
> take him;
>the guy is not only smart, but he also has a very strong math background.
>If the guy chokes and remains choked, still take him. He is still in the first
> 10%
>of population.
>
>
>But I don't understand why do you need intelligence for a DBA ? ;-)
>
>
>
>(*) Claude Shannon - The guy who invented a big chunk of information theory.
>
I have another extension.
If the PERSON answered correct to the first question, you can ask THEM quickly:
What about nine balls?
If they get it wrong, don't take them, because they already knew the answer to the first question when they came in to the interview. Otherwise, they would get the answer quickly.
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