Question

a new sidewalk will be 4 feet wide, 160 feet long, and filled to a depth of 3 inches (0.25 foot) with concrete. how many cubic yards of concrete are needed?
the new sidewalk needs cubic yards of concrete. (round to one decimal place as needed.)

Explanation:

Step1: Calculate volume in cubic feet

The volume $V$ of a rectangular - prism (which the sidewalk resembles) is given by the formula $V = l\times w\times h$, where $l = 160$ feet, $w = 4$ feet, and $h=0.25$ feet.
$V = 160\times4\times0.25$
$V = 160$ cubic feet.

Step2: Convert cubic feet to cubic yards

Since 1 cubic yard is equal to 27 cubic feet ($1$ yard = 3 feet, so $(1\text{ yard})^3=(3\text{ feet})^3 = 27\text{ cubic feet}$), we divide the volume in cubic feet by 27 to get the volume in cubic yards.
Let $V_y$ be the volume in cubic yards. Then $V_y=\frac{V}{27}$.
$V_y=\frac{160}{27}\approx5.9$ cubic yards.

Answer:

$5.9$