A washer (flat ring) is cut out of a circular sheet of metal. A program is needed to calculate the surface area of the resulting washer. The image shows the completed washer in grey.

The required formulae are:

$$area\; of\; outer\; circle=\pi R^2$$ $$area\; of\; inner\; circle=\pi r^2$$ $$surface\; area\; of\; washer=area\; of\; outer\; circle-area\; of\; inner\; circle$$

• $R$ is the radius of the outer circle
• $r$ is the radius of the inner circle
• $\pi$ is the constant Pi.

The table shows accurate test results for two sets of inputs.

The program has these requirements:

• the outer radius is an integer
• the inner radius is an integer
• the user inputs both the outer radius and the inner radius (no validation required)
• the inner radius must be strictly smaller than the outer radius to make a valid washer
• the variables supplied in the code file must be used.

Below is the content of the file Q03.py:

import math

outer_radius = int(input("Enter outer radius: "))
inner_radius = int(input("Enter inner radius: "))

# Calculate area
area_outer = math.pi * (outer_radius ** 2)
area_inner = math.pi * (inner_radius ** 2)

print(area_outer - area_inner)