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#Post#: 2482--------------------------------------------------
Math question...
DIR By: Michel
Date: April 14, 2013, 3:40 pm
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Surely, some of us here must love mathematics, so here's one you
might want to take a bite at.
First: The correct answer to this question is worth +5, and you
must show a bit of a working....
here we go:
assume that a snowball melts so that its volume decreases at a
rate proportional to its surface area, I f it takes 3 hours for
the snowball to decrease to half its original volume, how much
longer will it take for the snowball to melt completely?
#Post#: 2485--------------------------------------------------
Re: Math question...
DIR By: Chemist@
Date: April 16, 2013, 6:29 am
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I am not sure, but I will give it a shot:
3 hours for half of the ball to melt. The surface is halved and
for the new surface to melt to half, 1.5 hours need to pass.
This repeats many times and we have to calculate the sum of the
regression:
3/2+3/4+3/8+3/16+...... which is ≈3h.
3h are needed so it can melt completely.
#Post#: 2487--------------------------------------------------
Re: Math question...
DIR By: Michel
Date: April 16, 2013, 8:21 am
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--- Quote from: Chemist@ link ---
>
> I am not sure, but I will give it a shot:
> 3 hours for half of the ball to melt. The surface is halved
and for the new surface to melt to half, 1.5 hours need to pass.
This repeats many times and we have to calculate the sum of the
regression:
> 3/2+3/4+3/8+3/16+...... which is ≈3h.
> 3h are needed so it can melt completely.
>
--- End Quote ---
nice to see your attempt, chemist@, sounds logical on the
surface, but if you look closely at the statement
--- Quote from: Michel link ---
>
>
> assume that a snowball melts so that its volume decreases at a
rate proportional to its surface area,
>
--- End Quote ---
you could get some new insights?
The problem is still open :)
#Post#: 2488--------------------------------------------------
Re: Math question...
DIR By: Cheminized
Date: April 16, 2013, 12:18 pm
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i couldn't solve it without introducing another assumption, but
any way i thought I'd give it a try.. ;D
i used MWord for the mathematical convenient.. >:( >:(
#Post#: 2494--------------------------------------------------
Re: Math question...
DIR By: Michel
Date: April 17, 2013, 4:48 am
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--- Quote from: Cheminized link ---
>
> i couldn't solve it without introducing another assumption,
but any way i thought I'd give it a try.. ;D
> i used MWord for the mathematical convenient.. >:( >:(
>
--- End Quote ---
nicely worked out, simply subtracting 3h from your solution
gives the time we're looking for ;)
nice job!
#Post#: 2498--------------------------------------------------
Re: Math question...
DIR By: Cheminized
Date: April 17, 2013, 11:40 am
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come on bro, where is my +5???!!! ??? ??? ???
#Post#: 2511--------------------------------------------------
Re: Math question...
DIR By: Michel
Date: April 21, 2013, 7:29 am
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--- Quote from: Cheminized link ---
>
> come on bro, where is my +5???!!! ??? ??? ???
>
--- End Quote ---
Done:)
#Post#: 2515--------------------------------------------------
Re: Math question...
DIR By: Cheminized
Date: April 22, 2013, 11:34 pm
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it's not me bro, it's my brain who kept asking the awards
center in it for his treat,,, ;D
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