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About 1.15 million people live in a circular region with a population density of about 18,075 people per square kilometer. Find the radius of the region

 Sep 15, 2017
 #1
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density area people

About 1.15 million people live in a circular region

with a population density of about 18,075 people per square kilometer.

Find the radius of the region

 

Let A = area of the circular region
Let r = radius of the circular region

 

A= ?

A=1500000 people×1 km218075 people=150000018075 km2=82.9875518672 km2

 

r= ?

π r2=Ar2=Aπr=Aπ=82.9875518672π=26.4157581895r=5.13962626944 km

 

The radius of the region is 5.14 km

 

laugh

 Sep 15, 2017
edited by heureka  Sep 15, 2017
 #2
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heureka made a simple mistake in copying:

1.15 million / 18,075 =63.6238 Sq. Km- The area of the city region.

63.6238 = Pi x r^2

r^2 = 63.6238 / Pi

r^2 =20.252   take the sqrt of both sides

r = ~4.50 Km radius of the region

 Sep 15, 2017

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