Answer:
Exact Circumference = 4pi feet
Approximate Circumference = 12.56 feet (when using pi = 3.14)
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Step-by-step explanation:
The larger circle has a 3 foot radius.
The inner circle has a 3-1 = 2 foot radius.
Let's find the circumference of the smaller inner circle, which represents the glass window and ignores the metal frame surrounding it.
C = 2pi*r
C = 2pi*2
C = 4pi
The exact circumference is 4pi feet. This is the perimeter around the circle.
If you wanted, you can use an approximation like pi = 3.14 to find that 4pi = 4*3.14 = 12.56 feet is the approximate circumference.