STEP 1: find side $ a $
To find side $ a $ use formula:
$$ r = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $r = 72.8\, \text{cm}$ we have:
$$ 72.8\, \text{cm} = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = 72.8\, \text{cm} \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = 145.6\, \text{cm} $$ $$ a = \dfrac{ 145.6\, \text{cm} }{ \sqrt{ 3 } } $$ $$ a \approx 84.0622\, \text{cm} $$STEP 2: find perimeter $ P $
To find perimeter $ P $ use formula:
$$ P = 6 \cdot a $$After substituting $a = 84.0622\, \text{cm}$ we have:
$$ P = 6 \cdot 84.0622\, \text{cm} $$ $$ P \approx 504.3732\, \text{cm} $$