<p><span class="math-container">$\text{Poulation density} = \frac{\text{Population}}{\text{Surface}}$</span></p>

<p>Re-arranging </p>

<p><span class="math-container">$\text{Surface} = \frac{\text{Population}}{\text{Poulation density}}$</span></p>

<p>In your case</p>

<p><span class="math-container">$\text{Surface} = \frac{100,000,000\, \text{inhabitants}}{10\, \text{inhabitants}\, \text{km}^{-2}}=10,000,000\, \text{km}^2$</span></p>

<p>So something doesn't make sense, because those numbers suggests that the surface of the country is now larger than before.</p>

CC BY-SA 4.0
2019-02-07T08:24:55.893Z
Oh Camilo, where's your imagination? There could be an off shore volcano creating land. :-). All joking aside, I agree with you, the numbers in the question don't make sense. I think the population densities are wrong.
Fred
CC BY-SA 4.0
2019-02-07T01:14:16.547Z
2019-02-07T01:14:16.547Z
Camilo Rada
<p>I am not sure if the question suits in this stack board, but I give it a try.</p>

<p>Let's assume there is a country with a population of <strong>327 million people</strong> and a surface of <strong>9.6 million km²</strong>, resulting in <strong>34 inhabitants per km²</strong>. </p>

<p>Now, let's say we have a fictive war scenario, in which the country loses and has to give up land to the victors. The population sunk to <strong>100 million people</strong> and <strong>10 inhabitants per km²</strong> (still assuming that surface was given to victors, thus the country now has a smaller surface!!). How would I calculate the new surface with these two (now changed) variables or would I need more data?</p>

<p>My question now is: </p>

<p><em>Is it still possible to determine the new surface of the country when both population and population density changed?</em> </p>

<p>I tried many ways to accomplish that, but I really have no idea how to approach it. Maybe it's possible with a system of linear equations? I have no idea.</p>

CC BY-SA 4.0
2019-02-08T10:56:59.890Z
was americas land area  smaller before the europeans discovered it,it is related to the logic of your question.
trond hansen
CC BY-SA 4.0
2019-02-10T14:03:00.060Z
Sorry but this has noting to with Earth Science. It's an elemental math question. If X/Y=Z, and I know X and Z, can I calculate Y? Of course you can.
Jan Doggen
CC BY-SA 4.0
2019-02-11T08:51:54.767Z
I'm voting to close this question as off-topic because it just a mathematical question that has nothing to do with Earth Science
Jan Doggen
<geography><mathematics>
How to determine (lost) surface (km²) of a country when both population and population density have changed?
Caje
# How to determine (lost) surface (km²) of a country when both population and population density have changed?

(Asked by: username_0 on 2019-02-07)

I am not sure if the question suits in this stack board, but I give it a try.

Let's assume there is a country with a population of **327 million people** and a surface of **9.6 million km²**, resulting in **34 inhabitants per km²**.

Now, let's say we have a fictive war scenario, in which the country loses and has to give up land to the victors. The population sunk to **100 million people** and **10 inhabitants per km²** (still assuming that surface was given to victors, thus the country now has a smaller surface!!). How would I calculate the new surface with these two (now changed) variables or would I need more data?

My question now is:

*Is it still possible to determine the new surface of the country when both population and population density changed?*

I tried many ways to accomplish that, but I really have no idea how to approach it. Maybe it's possible with a system of linear equations? I have no idea.

**Tags:** geography, mathematics

> **Comments:**
> **username_1**: was americas land area  smaller before the europeans discovered it,it is related to the logic of your question.  
> **username_2**: Sorry but this has noting to with Earth Science. It's an elemental math question. If X/Y=Z, and I know X and Z, can I calculate Y? Of course you can.  
> **username_2**: I'm voting to close this question as off-topic because it just a mathematical question that has nothing to do with Earth Science  

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## 1 answers

### Answer by username_3 on 2019-02-07. Score: 3

$\text{Poulation density} = \frac{\text{Population}}{\text{Surface}}$

Re-arranging

$\text{Surface} = \frac{\text{Population}}{\text{Poulation density}}$

In your case

$\text{Surface} = \frac{100,000,000\, \text{inhabitants}}{10\, \text{inhabitants}\, \text{km}^{-2}}=10,000,000\, \text{km}^2$

So something doesn't make sense, because those numbers suggests that the surface of the country is now larger than before.

> **Comments:**
> **username_4**: Oh username_3, where's your imagination? There could be an off shore volcano creating land. :-). All joking aside, I agree with you, the numbers in the question don't make sense. I think the population densities are wrong.  

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