# Thread: Approximation Based on Area

1. ## Approximation Based on Area

Hey Fellows,

I am having trouble coming up with a solution of a problem related to area, popoulation, and Number of Houses. So here's what I am trying to do.

I have:
Area of a City
Population of a City
Number of Buildings in a City

Based on this information I want to approximate few scenarios based on flooding. Lets say the city is flooded and significant portion of the city is under water. I know how much area is lost due to flooding. So how can I then approximate the number of people who are affected and number of buildings which are under water? Is there any mathetical name for problem as such, and what kind of formula, function or method would you recomend?

Any help will be appreciable.

Regards.

2. ## Re: Approximation Based on Area

Should be able to do a fairly straightforward process to solve this one. If you assume that people and buildings are evenly distributed though-out your area, then you can take the percentage flooded times the total number of buildings and people to figure the amount lost. Since people and buildings cluster together, it would likely improve your result to treat the areas differently. If you know enough about it, can you separate the area into (maybe) three area types (dense, moderate, sparse) and weight them accordingly (still summing to your original number)? If so, use the exact same method but weight accordingly. Hope this helps.

3. ## Re: Approximation Based on Area

Thank you for your prompt reply. Lets see if I understand fully what you suggested.
So lets say the Area of the City is 100 Km2, population is 500, and 75% of the area is lost. So I am multiplying 75% with 500 to get 350?
If so what do we call this method as I will have to state this in the methodology.

Cheers!

4. ## Re: Approximation Based on Area

Looks like you've got it. The area of the city isn't required, since you already know the percentage lost, and you are assuming that people and buildings are an equal distance apart. 75% lost * 500 people = 375 people lost. I don't know what the name of this method would be if it has one. Something like an 'expected weighted value' maybe.

5. ## Re: Approximation Based on Area

Originally Posted by Will57
Looks like you've got it. The area of the city isn't required, since you already know the percentage lost, and you are assuming that people and buildings are an equal distance apart. 75% lost * 500 people = 375 people lost. I don't know what the name of this method would be if it has one. Something like an 'expected weighted value' maybe.
Yes I meant 375, well thanks a lot for your help.

6. ## Re: Approximation Based on Area

Originally Posted by SteveCuda
...
If so what do we call this method as I will have to state this in the methodology.
... have a look here: Cross-multiplication - Wikipedia, the free encyclopedia