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June 12, 2026, 01:44:26 pm
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Author Topic: help?`  (Read 1797 times)  Share 

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wombifat

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help?`
« on: July 11, 2009, 07:54:23 pm »
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I don't know if I'm just a bit rusty or the question is weird but i can't work this one out

Water is draining from a cone-shaped funnel at a rate of 500cm^3/min. THe cone has a base radius of 20cm and height of 100cm. Let hcm be the depth of water at time t minutes. The rate of decrease of h in cm\min is given by...
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TrueTears

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Re: help?`
« Reply #1 on: July 11, 2009, 08:01:57 pm »
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Volume of a cone is

Draw a cone using similar triangles:











Remember when you answer in words, it is decreasing at a rate.. blah blah... take off the -.
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PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.

dcc

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Re: help?`
« Reply #2 on: July 11, 2009, 08:03:18 pm »
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Since the question asks for the rate of decrease, I assume they want the absolute value of the answer provided.
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wombifat

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Re: help?`
« Reply #3 on: July 11, 2009, 08:03:25 pm »
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ok thanks that helps
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TrueTears

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Re: help?`
« Reply #4 on: July 11, 2009, 08:03:50 pm »
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Quote from: dcc on July 11, 2009, 08:03:18 pm
Since the question asks for the rate of decrease, I assume they want the absolute value of the answer provided.
I said that.
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dcc

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Re: help?`
« Reply #5 on: July 11, 2009, 08:09:44 pm »
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... after you edited your post, yes.
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TrueTears

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Re: help?`
« Reply #6 on: July 11, 2009, 08:11:19 pm »
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Quote from: dcc on July 11, 2009, 08:09:44 pm
... after you edited your post, yes.
I added it 1 second after I pressed post. I need to preview more.
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PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.

wombifat

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Re: help?`
« Reply #7 on: July 12, 2009, 02:43:27 pm »
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yeah thats what I got but the book was multiple choice and that wasn't an option. I'll just assume it's the book's fault.
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