Answer
The cost of concrete for a walkway is\[\$80\].
Work Step by Step
Calculate the volume of the concrete as follows:
\[\begin{align}
& \text{volume of the concrete}=27\text{ ft}\times 4\text{ ft}\times \frac{1}{12}\text{ft} \\
& =54\text{ f}{{\text{t}}^{3}}
\end{align}\]
It is know that 1 cubic yard is equal to 27 cubic feet.
Convert the cubic feet into yard as follows:
\[\begin{align}
& \text{54 f}{{\text{t}}^{3}}=\text{54 }f{{t}^{3}}\times \frac{1\text{ y}{{\text{d}}^{3}}}{27\text{ }f{{t}^{3}}} \\
& =\frac{54}{27}\text{ y}{{\text{d}}^{3}} \\
& =2\text{ y}{{\text{d}}^{3}}
\end{align}\]
Now, compute the cost as follows:
\[\begin{align}
& \text{Cost of the concrete}=2\text{ y}{{\text{d}}^{3}}\times \$40\\&=\$80\end{align}\]
Hence, the cost of concrete for a walkway is\[\$80\].
