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Math Help - Population Relative Growth Rate Concept?

  1. #1
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    Population Relative Growth Rate Concept?

    I got confused by the concept of relative growth rate and growth rate. I understand that when it says "relative growth rate of the population is 3%", it means dP/dt = 0.03P.
    However, when it says "growth rate of the population is 3%", does it mean:
    dP/dt = 0.03P
    or
    dP/dt = 0.03?

    To me the phrase "growth rate" seems more like a rate than a constant. Can someone help me out please?
    Thanks in advance!
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  2. #2
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    Re: Population Relative Growth Rate Concept?

    Hey LLLLLL.

    It means 0.03P since a 3% increase is 100% + 3% but since its is a derivative we look at the change which is 0.03P.
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    Re: Population Relative Growth Rate Concept?

    Quote Originally Posted by chiro View Post
    Hey LLLLLL.

    It means 0.03P since a 3% increase is 100% + 3% but since its is a derivative we look at the change which is 0.03P.
    Hi Chiro,
    Thank you so much for your reply!
    I get that the rate is going to contain 0.03. But I'm still a bit confused about why the rate depends on P.
    I'm not sure whether the phrase "growth rate of the population is 3%" means that the rate is constantly 0.03 or is 3% of the current population.
    Thank you again for your help!
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  4. #4
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    Re: Population Relative Growth Rate Concept?

    It is something like

    \frac{dP}{dt}=aP

    where a does not depend on t nor P. This kind of models are called Malthusian Malthusian growth model - Wikipedia, the free encyclopedia
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    Re: Population Relative Growth Rate Concept?

    Quote Originally Posted by LLLLLL View Post
    I got confused by the concept of relative growth rate and growth rate. I understand that when it says "relative growth rate of the population is 3%", it means dP/dt = 0.03P.
    However, when it says "growth rate of the population is 3%", does it mean:
    dP/dt = 0.03P
    or
    dP/dt = 0.03?

    To me the phrase "growth rate" seems more like a rate than a constant. Can someone help me out please?
    Thanks in advance!
    It has to be dP/dt = 0.03P, since it's 3%, and you never do a percent unless it's the relative growth rate.

    - Hollywood
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    Re: Population Relative Growth Rate Concept?

    Quote Originally Posted by Ruun View Post
    It is something like

    \frac{dP}{dt}=aP

    where a does not depend on t nor P. This kind of models are called Malthusian Malthusian growth model - Wikipedia, the free encyclopedia
    Thank you for that link!
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