Geometry

Question Analysis

The main focus is using the formula for the area of a ring. Given the outer and inner diameters,  we must first find the corresponding radii and then calculate the difference between the areas of the outer and inner circles.

 

Key Concept Explanation

The area of a circle is , where  is the radius. For a ring, the area , with  as the outer radius and  as the inner radius. This formula is based on subtracting the area of the inner circle from the area of the outer circle.

 

Step - by - Step Solution

1. Calculate the radii:

The outer radius , and since  ft,  ft.

The inner radius , and since  ft,  ft.

2. Apply the ring - area formula:

Substitute into