# rates change

Hi ,

I need help with getting the method for the  answer to these 2 questions.

4f) 9.5 mins
exam1.docx
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Commented:
volume / flow rate
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Author Commented:
there are 2 questions and could you be more specific about the numbers?
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Commented:
4e Volume of the cone at 2m  /  0.2m^3/min
4f seems to be missing some outflow rate information
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Author Commented:
4f isnt missing information
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Commented:
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RetiredCommented:
The volume of a cone is: (pi * r^^2 * h) / 3 ...

To answer e) calculate the volume of THIS cone when h = 2 meters then divide the answer by 0.2 m^^3/minute to get the answer in minutes.

To answer f), you have to know at what rate the liquid drains from the inverted come (i.e. as soon as the tank is empty, the tap turns itself off..., but this information cannot be found on the question you gave us!

But it is the same deal: calculate the volume of THIS cone when h = 2 meters then divide the answer by volume of draining/minute to get the answer in minutes.

Add the 2 answers e) + f) together to find out what the total time is!
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Information Technology SpecialistCommented:
We can only assume that 4b), 4c), or 4d) provided some information that gives, or allows for the computation of, the outflow rate for 4f) and really can't help any further for that question without it. Do you still need additional information for 4e)? Is this an assignment or test you need to complete or are you just looking for the justification for those given answers?
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RetiredCommented:
@jagguy >>4f isnt missing information

As everyone keeps mentioning, you must know what the rate of flow when the cone drains, otherwise you cannot find the answer to the question!
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Author Commented:
The whole public exam is here  . I uploaded this before and it was taken down for copyright  reasons even though it is public information.

http://www.vcaa.vic.edu.au/Documents/exams/mathematics/2012/2012mmcas2-w.pdf
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RetiredCommented:
Solving this equation for t when h = 2 metres will give you the time it takes for the tank to drain when the height is 2 metres.

Now you have all the information to solve part f).
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