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Last Updated on May 5, 2023
GMAT OFFICIAL GUIDE PS
Solution:
The circular path (i.e., the shaded region) is called an annulus in geometry. Basically an annulus is a ring-shaped figure bounded by two concentric circles. To find the area of an annulus we use the formula:
π(radius(2)^2 – radius(1))^2
where radius(1) is the radius of the inner circle and radius(2) is the radius of the outer circle.
The formula is highlighted in the diagram below.
We know:
radius(2) = 8 + 3 = 11 feet
radius(1) = 8 feet
Plugging into our equation we have:
area = π(11^2 – 8^2)
area = π(121 – 64)
area = 57π
Answer: D
