Find the volumes of the two cones and subtract.
V = 1/3 * pi * r^2 * h
V = 1/3 * 3.14 * 6^2 * 9
Simplify exponent:
V = 1/3 * 3.14 * 36 * 9
Multiply:
V = 339.12
V = 1/3 * pi * r^2 * h
V = 1/3 * 3.14 * 3^2 * 6
Simplify exponent:
V = 1/3 * 3.14 * 9 * 6
Multiply:
V = 56.52
Subtract the two volumes:
339.12 - 56.52 = 282.6
So the Garden Landscaping Company purchased 282.6 ft^3 of gravel.