# Math Help - Population Relative Growth Rate Concept?

1. ## 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?

2. ## 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.

3. ## Re: Population Relative Growth Rate Concept?

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!

4. ## 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

5. ## Re: Population Relative Growth Rate Concept?

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

6. ## Re: Population Relative Growth Rate Concept?

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