conversion of units

Question

The Harris family needs to purchase topsoil for their landscaping project (measuring 50 ft x 40 ft with a thickness of 6 inches of topsoil/mulch). They have two options: a) purchasing the soil in 3 ft3 bags priced at $2.25 each with no delivery charge, or b) purchasing in bulk at $18 per cubic yard with a one-time $50 delivery fee. Which option is the least expensive and by how much? Explain.

Answer 1

First calculate how much they will need

converting the 6 inches =0.5 ft

50 * 40 * 0.5 = 1000 ft³

Option : a)

(1000 / 3)* 2.25 = $750

Option : b)

Convert cubic feet to cubic yards by the formula

yd³ = ft³ * 0.037037

1000 * 0.037037 = 37.037

(37.037 * 18) + 50 = $716.66

So option b is cheaper.