Answer
The width of the concrete boarder $=2.71$ feet
Work Step by Step
We know the area of the concrete is equal the following equation
$\pi*(5+x)^2-\pi*5^2=A$
Volume is just area times the height and height = 3 inches=.25 feet so
$27=.25*(\pi*(5+x)^2-\pi*5^2)$
$27=.25\pi*((x^2+10x+25)-25)$
$27=.25\pi*(x^2+10x)$
Letting $\pi$=3.14
$x^2+10x=34.377$
Solve using the quadratic formula to find $x=2.71$ feet.
