STEP 1: find side $ a $
To find side $ a $ use formula:
$$ r = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $ r = \frac{ 16 }{ 125 } $ we have:
$$ \frac{ 16 }{ 125 } = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = \frac{ 16 }{ 125 } \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = \frac{ 32 }{ 125 } $$ $$ a = \dfrac{ \frac{ 32 }{ 125 } }{ \sqrt{ 3 } } $$ $$ a = \frac{ 32 \sqrt{ 3}}{ 375 } $$STEP 2: find diagonal $ d $
To find diagonal $ d $ use formula:
$$ d = 2 \cdot a $$After substituting $ a = \frac{ 32 \sqrt{ 3}}{ 375 } $ we have:
$$ d = 2 \cdot \frac{ 32 \sqrt{ 3}}{ 375 } $$ $$ d = \frac{ 64 \sqrt{ 3}}{ 375 } $$