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Six small circles, each of radius 3 units, are tangent to a large circle as shown. Each small circle also is tangent to its two neighboring small circles. What is the diameter of the large circle in units?

 

 

Thanks!

AnonymousConfusedGuy  Mar 29, 2018
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Connecting the centers  of the smaller circles  forms a hexagon  with  sides  of  6  units

 

But segments drawn from the center of the larger circle to each of these  6 centers  will form 6 equilateral triangles......so....a side of one of these triangles =  the side of the hexagon  =  6 units  (1)

 

And the distance from  a smaller circle center to the edge of the larger circle  = the radius of a smaller circle   = 3 units   (2)

 

So....the radius of the larger circle  =  (1)  + (2)  =    6 + 3  =   9 units

 

So...its diameter  =  2 * 9    =    18 units

 

 

cool cool cool

CPhill  Mar 29, 2018

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