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Bunuel
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Bunuel
In the figure below, the centers of all three circles lie on the same line. The medium-sized circle has a radius twice the size of the radius of the smallest circle, and the smallest circle has a radius whose length is 2. What is the area of the shaded region?


(A) 3π
(B) 4π
(C) 6π
(D) 8π
(E) 10π


Attachment:
2020-12-21_21-18-40.png

To figure out the area of the shaded region we need to determine half of the areas of each circle and deduct the sum half of the areas of the smaller and medium from the half of the area of the largest area.


The radius of the smaller circle \(2; \ area = πr^2=π2^2=4π; \ half = 2π\)

The radius of the Medium circle \(4; \ area = πr^2=π4^2=16π; \ half = 8π\)

The radius of the Largest circle \(\frac{8+4}{2}=6; \ area = πr^2=π6^2=36π; \ half = 18π \)[The smaller and medium circle comprise the largest circle, so the sum of the diameters of the smaller circle and medium circle is the diameter of the largest circle.]

The area of the shaded region \(=18π-2π-8π=8π\)

The answer is \(D\)
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Area of the Shaded Region will be given by:

(1/2) * [Area of Largest Circle - (Area of Small Circle + Area of Medium Circle)]


Radius of Small Circle = 2

Since Radius of Medium Circle is twice the length, Radius of Medium Circle = 4


Since all 3 Center are on the same horizontal line across the Center of the Circles:

Diameter of Large Circle = (Diameter of Small Circle) + (Diameter of Medium Circle)

Diameter of Large Circle = (4) + (8) = 12
Radius of Large Circle = 6


Shaded Region Area =

(1/2) * [ (6)^2 * (pi) - [ (2)^2 * (pi) + (4)^2*(pi) ] ]

(1/2) * [36(pi) - [4(pi) + 16(pi)] ]

(1/2) * [36(pi) - 20(pi)]

(1/2) * (16(pi))

8(pi)

(D)
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