We are told that a tunnel opening has the shape of the following semicircle.
We want to find the area of the tunnel opening. Recall that the area A of a semicircle equals half the product of π and the square of its radius r.
A = 1/2 π r^2
Since the diameter of the tunnel opening is 23 feet, the radius of the tunnel opening is ( 12* 23) feet or 11.5 feet. Let's calculate the area using this information. We can use 3.14 as an estimation of π.
