STEP 1: find radius $ r $
To find radius $ r $ use formula:
$$ C = 2 \cdot r \cdot \pi $$After substituting $ C = \frac{ 197 }{ 10 } $ we have:
$$ \frac{ 197 }{ 10 } = 2 \cdot r \cdot \pi $$ $$ r = \dfrac{ \frac{ 197 }{ 10 } }{ 2 \pi } $$ $$ r \approx 3.1354 $$STEP 2: find diameter $ d $
To find diameter $ d $ use formula:
$$ d = 2 \cdot r $$After substituting $ r = 3.1354 $ we have:
$$ d = 2 \cdot 3.1354 $$ $$ d \approx 6.2707 $$