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Geometry Level 2

What's the area of the main square?


The answer is 256.

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4 solutions

Daniel Liu
Jun 2, 2014

Let the radius of the big circle be r r . By Power of a Point, we have r ( r 6 ) = ( r 4 ) 2 r(r-6)=(r-4)^2 Solving this equation gives r = 8 r=8 . Thus, the area of the square is ( 2 r ) 2 = 256 (2r)^2=\boxed{256} .

Oh I used Altitude Theorem.

Finn Hulse - 7 years ago
Rouge Santillan
Feb 21, 2015

6 is 3/4 of the half, 4 is 1/2, so 1/4 of half is 2. 6+2=8(2)= 16. area of square is equal to side times side so (16)(16)=256

Fox To-ong
Jan 21, 2015

diameter = 6 + 6 + 4 = 16 = 2r = side of the square

Finn Hulse
Jun 2, 2014

Notice how an inscribed triangle can be drawn in the smaller circle by connecting the three bold dots. From our knowledge of circles, we can see that this is a right triangle. Let the radius of the larger circle be r r . From the Altitude theorem, we can construct:

( r 6 ) ( r ) = r 4 \sqrt{(r-6)(r)}=r-4

Squaring and ignoring the extraneous solution produces

r 2 6 r = r 2 8 r + 16 r^2-6r=r^2-8r+16

2 r = 16 2r=16

r = 8 r=8

We see that the side length of the square is 2 r 2r , or 16 16 , and thus the area is 1 6 2 = 256 16^2=\boxed{256} . Great problem @Mardokay Mosazghi ! :D

@Finn Hulse Thanks not an original problem

Mardokay Mosazghi - 7 years ago

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It's okay dude. Brilliant is about sharing problems, not necessarily writing them (all the time). :D

Finn Hulse - 7 years ago

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