Question 1041813
We have an equilateral triangle with four circles on a side
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draw a horizontal line connecting the four centers and draw a perpendicular line from the center of each circle on the ends(there are two) to the side.
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label(AB) the distance from each end to the intersection point of the perpendicular line and the side
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side length = 2AB + 6r, where r is the radius of a circle
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note the angles in the triangles formed at each end are 30, 60, 90 with the AB's opposite the 60 degree angles
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the sides in a 30-60-90 are in the ratio 1:square root(3):2, therefore
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AB = r*square root(3) and we have
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20 = 2r*square root(3) + 6r
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10 = r * square root(3) + 3r
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r = 10 / (square root(3) + 3) = 2.1132 cm
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