Question

A unit of area often used in measuring land areas is the hectare, defined as 104 m2. An open-pit coal mine consumes 75 hectares of land, down to a depth of 26 m, each year. What volume of earth, in cubic kilometers, is removed in this time?

Answer 1

Answer:

$0.0195km^{3}$

Explanation:

1 hectare = 10^4 m^2

Area of pit, A = 75 hectare

convert hectare into m^2

A = 75 x 10^4 m^2

depth, d = 26 m

Volume of earth removed is V.

V = area of pit x depth

V = A x d

V = 75 x 10^4 x 26 = 1950 x 10^4 m^3

Convert cubic metre into cubic km

1 m = 10^-3 km

1 m^3 = 10^-9 km^3

So,

$V = 1950 \times 10^{4} \times 10^{-9}=0.0195km^{3}$