Calculating Volume of Earth Removed in Open-Pit Coal Mine

[lgen0290]

Homework Statement

A unit of area, often used in measuring land areas, is the "hectare", defined as 104 m2. An open-pit coal mine consumes 80 hectares of land, down to a depth of 26 m, each year. What volume of earth, in cubic kilometers, is removed in this time?

Homework Equations

The Attempt at a Solution

I calculated the area to be a square, with each side being .8944(sqrt of 800,000 divided by 1000). I multiplied this by .026. It gave me .0232. Ths answer is not correct.

 

[spizma]

Heres a hint:

I would start by figuring out how many kilometers squared there are per hectare, and then multiplying by 80. If you know that then you already have the top area converted to km. You seem like you know what you should do from there.

 

[lgen0290]

OK, there is .1km squared per hectacre. I multiplied by 80, then by .026. I got .208, which is not correct.

 

[spizma]

Your conversion from hectares to km^2 is incorrect. To figure out what is correct start with the equation 1,000,000 m^2 = 1 km^2. Then convert the 1 million m^2 to hectares, and then solve for how many km^2 are in one hectare.

 

[kamerling]

OK, there is .1km squared per hectacre.

this is not correct