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OfflineRainman420
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Registered: 06/05/06
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Calculus 2 anyone. (Please help)
    #11235016 - 10/12/09 08:45 PM (8 years, 3 months ago)

So I have a huge test tomorrow and I am not getting this stuff.

Here are two problems from exponential growth and decay.

1. A bacteria culture grows with constant relative growth rate. After 2 hours there are 600 bacteria and after 8 hours the count is 75,000. Find the initial population.
For this one the formula im using is P=A0ekt

2. Bismuth-210 has a half life of 5 days. A sample originally has a mass of 800mg. When is the mass reduced to 1mg?
I have no idea what I'm doing on this one.

Please help I have a big test tomorrow. If anyone can give me extra help through AIM or messenger or something, feel free to send me a pm.


--------------------
The average age of the world's greatest civilizations from the beginning of history has been about 200 years. During those 200 years, these nations always progressed through the following sequence:

From bondage to spiritual faith;
From spiritual faith to great courage;
From courage to liberty;
From liberty to abundance;
From abundance to selfishness;
From selfishness to complacency;
From complacency to apathy;
From apathy to dependence;
From dependence back into bondage.


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Offlinelearningtofly
Ancient Aliens
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Registered: 05/21/07
Posts: 15,105
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Re: Calculus 2 anyone. (Please help) [Re: Rainman420]
    #11235054 - 10/12/09 08:51 PM (8 years, 3 months ago)

u gotta find the derivatives brah.


--------------------


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,200
Re: Calculus 2 anyone. (Please help) [Re: Rainman420]
    #11235164 - 10/12/09 09:10 PM (8 years, 3 months ago)

1)Here you have two unknowns, A and k.  First you need to find k, then you can find A.  To find k you are gonna have to use a logarithm (the natural logarithm).  Treat the 600 bacteria as your initial amount (temporarily) and then your P will be 75,000 after 6 hours.  Plug those into the equation and solve for k (using the natural logarithm).  Once you know k, use the 2 hours to get 600 bacteria and solve for A.

2)  Two needs a half life forumula.  Different classes use different ones, so Im hesitant to start explaining.  You can use the same formula as in 1, you just have to find a different k.  Otherwise find some half life formula and plug your shit in then solve for t.

Is this calculus 2?  It seems like brief calc.


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OfflineRainman420
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Re: Calculus 2 anyone. (Please help) [Re: DieCommie]
    #11235247 - 10/12/09 09:28 PM (8 years, 3 months ago)

Thanks DieCommie awesome response. I got the first one. Anser was P=120

I'm working on the second one now.

Yeah its calc 2, these are actually the easier problems for this section of the test, lol.

For the second one i'm using m=m0e-kt

got any hints?


--------------------
The average age of the world's greatest civilizations from the beginning of history has been about 200 years. During those 200 years, these nations always progressed through the following sequence:

From bondage to spiritual faith;
From spiritual faith to great courage;
From courage to liberty;
From liberty to abundance;
From abundance to selfishness;
From selfishness to complacency;
From complacency to apathy;
From apathy to dependence;
From dependence back into bondage.


Edited by Rainman420 (10/12/09 09:31 PM)


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InvisibleLe_Canard
The Duk Abides


Registered: 05/17/03
Posts: 94,392
Loc: Earthfarm 1 Flag
Re: Calculus 2 anyone. (Please help) [Re: Rainman420]
    #11235284 - 10/12/09 09:34 PM (8 years, 3 months ago)

Good luck with that. I could never "get" Calculus, myself.


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,200
Re: Calculus 2 anyone. (Please help) [Re: Rainman420]
    #11235301 - 10/12/09 09:36 PM (8 years, 3 months ago)

Yea, recall the definition of a half life.  It means that half the stuff is gone after one half life.  So you can set m = (1/2)m0 (half your original stuff), then set t = (your half life time).  Then you can solve for the specific 'k' value of your half life time and use that to answer the question.


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InvisiblePJDIDDLE
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Registered: 10/17/02
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Re: Calculus 2 anyone. (Please help) [Re: DieCommie]
    #11235412 - 10/12/09 09:54 PM (8 years, 3 months ago)

.


Edited by PJDIDDLE (03/12/12 03:04 PM)


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,200
Re: Calculus 2 anyone. (Please help) [Re: PJDIDDLE]
    #11235428 - 10/12/09 09:56 PM (8 years, 3 months ago)

Yea, it went well.  Nothing too important got broken.  Im getting my ass kicked by school and hope all this has been worth it, but besides that Oregon is beautiful.  How is the valley and school treating you?


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InvisiblePJDIDDLE
Female
Registered: 10/17/02
Posts: 2,837
Re: Calculus 2 anyone. (Please help) [Re: DieCommie]
    #11235480 - 10/12/09 10:03 PM (8 years, 3 months ago)

.


Edited by PJDIDDLE (03/12/12 03:04 PM)


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OfflineRainman420
Music is my Life
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Registered: 06/05/06
Posts: 1,265
Last seen: 1 month, 30 days
Re: Calculus 2 anyone. (Please help) [Re: DieCommie]
    #11235752 - 10/12/09 10:37 PM (8 years, 3 months ago)

Quote:

DieCommie said:
Yea, recall the definition of a half life.  It means that half the stuff is gone after one half life.  So you can set m = (1/2)m0 (half your original stuff), then set t = (your half life time).  Then you can solve for the specific 'k' value of your half life time and use that to answer the question.




The problem is giving me the time in days, do i need to convert to years?

I can't seem to figure it out.


--------------------
The average age of the world's greatest civilizations from the beginning of history has been about 200 years. During those 200 years, these nations always progressed through the following sequence:

From bondage to spiritual faith;
From spiritual faith to great courage;
From courage to liberty;
From liberty to abundance;
From abundance to selfishness;
From selfishness to complacency;
From complacency to apathy;
From apathy to dependence;
From dependence back into bondage.


Post Extras: Print Post  Remind Me! Notify Moderator
OfflineRainman420
Music is my Life
Male User Gallery


Registered: 06/05/06
Posts: 1,265
Last seen: 1 month, 30 days
Re: Calculus 2 anyone. (Please help) [Re: Rainman420]
    #11235843 - 10/12/09 10:45 PM (8 years, 3 months ago)

Nevermind I got it.  About 48 days. Wow I was really over thinking this problem.

I'm gonna keep throwing out problems if u guys don't mind.


--------------------
The average age of the world's greatest civilizations from the beginning of history has been about 200 years. During those 200 years, these nations always progressed through the following sequence:

From bondage to spiritual faith;
From spiritual faith to great courage;
From courage to liberty;
From liberty to abundance;
From abundance to selfishness;
From selfishness to complacency;
From complacency to apathy;
From apathy to dependence;
From dependence back into bondage.


Post Extras: Print Post  Remind Me! Notify Moderator
OfflineRainman420
Music is my Life
Male User Gallery


Registered: 06/05/06
Posts: 1,265
Last seen: 1 month, 30 days
Re: Calculus 2 anyone. (Please help) [Re: Rainman420]
    #11235924 - 10/12/09 10:56 PM (8 years, 3 months ago)

A thermometer is taken from a room where the temp. is 20C to the outdoors, where the temp. is 5C. After one minute the thermometer reads 12C. What will the reading on the thermometer be after one more minute?


--------------------
The average age of the world's greatest civilizations from the beginning of history has been about 200 years. During those 200 years, these nations always progressed through the following sequence:

From bondage to spiritual faith;
From spiritual faith to great courage;
From courage to liberty;
From liberty to abundance;
From abundance to selfishness;
From selfishness to complacency;
From complacency to apathy;
From apathy to dependence;
From dependence back into bondage.


Post Extras: Print Post  Remind Me! Notify Moderator
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