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A unit of area, often used in measuring land areas, is the "hectare", defined as 104 m2. An open-pit coal mine consumes 72 hectares of land, down to a depth of 25 m, each year. What volume of earth, in cubic kilometers, is removed in this time?

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boffeemadrid

Answer:

0.018 km³

Explanation:

Area of land

[tex]A=72\times 10^4\ m^2[/tex]

D = Depth of land = 25 m

Volume is given by

[tex]V=AD\\\Rightarrow V=72\times 10^4\times 25\\\Rightarrow V=18000000\ m^3[/tex]

Converting to cubic kilometers

[tex]1\ m=\dfrac{1}{1000}\ km[/tex]

[tex]1\ m^3=\dfrac{1}{1000^3}\ km^3[/tex]

[tex]18000000\ m^3=18000000\times \dfrac{1}{1000^3}=0.018\ km^3[/tex]

The volume of Earth removed is 0.018 km³

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