Packing $12$ unit circles in an equilateral triangle

Packing 12 unit circles in an equilateral triangle

OwOUwUOwU, via Wikimedia Commons. CC BY-SA 4.0.

The side length of the smallest equilateral triangle into which $12$ unit circles can be packed.

Value: $4+4\sqrt{3}$ (≈10.9282)

Updates

Upper bound: $4+4\sqrt{3}$ (≈10.9282)
Reference unknown
[via Circles in Triangles, Erich Friedman]
1994 Lower bound: $4+4\sqrt{3}$ (≈10.9282)
Melissen in 1994
[via Circles in Triangles, Erich Friedman]