posted by Ethan .
A unit of area often used in measuring land areas is the hectare, defined as 104 m2. An open-pit coal mine consumes 99 hectares of land, down to a depth of 28 m, each year. What volume of earth, in cubic kilometers, is removed in this time?
volume: 99hectare*10^4 m^2/hectare*28m*(1km/10^3 m)3