See the calculations, explanations and results below.
1) The section to cover has tha shape of box with these dimensions:
length: 9.5 ft
width: 12 ft
depth: 4 inches
3) The volume of a box is calculated as:
V = length × witdth × depth
Since the depth is in inches convert to feet.
Conversion factor: 1 feet = 12 inches
⇒ depth = 4 in × 1 feet / 12 inches = 1/3 feet
Now, calculate the volume using feet:
V = 9,5 feet × 12 feet × 1/3 feet = 38 feet³
4) convert that to yard³ to compare with the calculations made by Rosilaine:
Conversion factor: 1 yard = 3 feet
⇒ 38 ft³ × (1 yard / 3 ft) ³ = (38 / 27) yard³ = 1.41 yard³
5) The error probably was that Rosailined used a wrong conversion factor.
Notice that 38 / 3 ≈ 12.7; so a likely mistake is that she did not cube the factor and so got about 12 yard³.
6) She might order 1.5 yard³ or 2.0 yard³ depending on the seller's rates and restrictions. With that she will have enough and will not have too much left over.
