Posted by **liz** on Wednesday, August 25, 2010 at 6:17pm.

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 29 m, each year. What volume of earth, in cubic kilometers, is removed in this time?

- physics -
**MathMate**, Wednesday, August 25, 2010 at 7:24pm
The volume of earth removed is a rectangular prism, the volume of which is the planar area multiplied by the depth.

V = 72 hectares * 29 m

= 72*104 m² * 29 m

= 72*104*29 m³

Now one cubic kilometer contains

(1000)³ m³

= 1,000,000,000 m³

All you need to do is to convert the previous answer into km³.

- physics -
**Mike**, Friday, September 3, 2010 at 5:02pm
.0207 km3

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