# Population Relative Growth Rate Concept?

• April 4th 2013, 08:38 PM
LLLLLL
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?
• April 4th 2013, 09:17 PM
chiro
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.
• April 4th 2013, 10:38 PM
LLLLLL
Re: Population Relative Growth Rate Concept?
Quote:

Originally Posted by chiro
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,
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!
• April 5th 2013, 03:47 AM
Ruun
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
• April 5th 2013, 07:38 AM
hollywood
Re: Population Relative Growth Rate Concept?
Quote:

Originally Posted by LLLLLL
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?

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
• April 6th 2013, 08:39 PM
LLLLLL
Re: Population Relative Growth Rate Concept?
Quote:

Originally Posted by Ruun
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