What is the formula to calculate the area of a concentric reducer?

The area of a concentric reducer can be calculated by finding the areas of the two circular ends (the larger and smaller diameters) and then taking the difference between them. The formula is:

[ \text{Area} = A_1 - A_2 = \pi \left( \left(\frac{D_1}{2}\right)^2 - \left(\frac{D_2}{2}\right)^2 \right) ]

where ( D_1 ) is the diameter of the larger end, and ( D_2 ) is the diameter of the smaller end.