## Elementary Technical Mathematics

$A=239~in^{2}$
The area of the side of the tire is the area of the outer circle minus the area of the inner circle. We use the area of a circle: $A=\frac{\pi*d^{2}}{4}$ With the two different diameters and subtract the difference. Thus, we have: $A=\frac{\pi*dout^{2}}{4}-\frac{\pi*din^{2}}{4}=\frac{\pi*(23in)^{2}}{4}-\frac{\pi*(15in)^{2}}{4}=238.76in^{2}\approx239~in^2$