Question 958499
inside walk radius=r=16 ft=5.33yd; outside walk radius=R=18ft=6yds
A=Area of walk=(area of outside circle)-(area of inside circle)
{{{A=((pi)R^2)-((pi)r^2)}}}
{{{A=(pi)(6yds)^2-(pi)}}}{{{(5.3yds)^2}}}
{{{A=36(pi)yd^2-28.4(pi)yd^2}}}
{{{A=7.6(pi)yd^2}}}={{{23.7yd^2}}}
Area x Thickness will give volume Thickness=0.083yds
{{{Volume=(23.74yd^2)(0.083yd)}}}={{{1.99yd^3}}}
ANSWER: You will need 1.99 yards of concrete for the walk.