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September 6th, 2015, 12:52 AM   #1
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Maths homework

Hi,
I can't get my head around this problem. Any help is appreciated.
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Last edited by skipjack; September 6th, 2015 at 01:11 AM.

 September 6th, 2015, 01:08 AM #2 Senior Member   Joined: Sep 2015 From: 4th Dimension Posts: 146 Thanks: 13 Math Focus: Everything (a little bit) It's easy. I will give you hints. First one tells the cost for given amount. Second one, try to remember $\displaystyle f'$ is the rate of change. I hope you find it. Last edited by skipjack; September 6th, 2015 at 01:13 AM.
 September 6th, 2015, 01:17 AM #3 Global Moderator   Joined: Dec 2006 Posts: 20,810 Thanks: 2153 Presumably, $f'\!(v)$ denotes the rate of change of $f(v)\!$ with respect to $v$.
September 6th, 2015, 01:24 AM   #4
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Quote:
 Originally Posted by skipjack Presumably, $f'\!(v)$ denotes the rate of change of $f(v)\!$ with respect to $v$.
I am not sure, but I feel it represents rate of change of cost when the amount is at 200 l

Last edited by skipjack; September 6th, 2015 at 08:25 AM.

 September 6th, 2015, 01:34 AM #5 Newbie   Joined: Sep 2015 From: australia Posts: 9 Thanks: 2 a) would be for 200 litres cost 4200$? b) I'm not getting the rates of change idea Last edited by skipjack; September 6th, 2015 at 08:28 AM. September 6th, 2015, 04:09 AM #6 Senior Member Joined: Dec 2012 From: Hong Kong Posts: 853 Thanks: 311 Math Focus: Stochastic processes, statistical inference, data mining, computational linguistics Quote:  Originally Posted by skitdemon a) would be for 200 litres cost 4200$?
Yep.

Quote:
 b) I'm not getting the rates of change idea
When you produce more and more chemical, the unit cost of the chemical will increase. f'(200) = 0.05 means that the cost increases at a rate of 0.05 when you are at your 200th litre of chemical.

If you plot the function on a graph, and draw a tangent at the point where x = 200, the slope of the tangent will be 0.05, which shows how fast the cost is increasing at that exact point.

Last edited by skipjack; September 6th, 2015 at 08:28 AM.

September 6th, 2015, 04:20 AM   #7
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Quote:
 Originally Posted by 123qwerty Yep. When you produce more and more chemical, the unit cost of the chemical will increase. f'(200) = 0.05 means that the cost increases at a rate of 0.05 when you are at your 200th litre of chemical. If you plot the function on a graph, and draw a tangent at the point where x = 200, the slope of the tangent will be 0.05, which shows how fast the cost is increasing at that exact point.
That's what I was saying.

Last edited by skipjack; September 6th, 2015 at 08:27 AM.

 September 6th, 2015, 08:17 AM #8 Newbie   Joined: Sep 2015 From: australia Posts: 9 Thanks: 2 I get it now, thanks!

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