STEP 1: find radius $ r $
To find radius $ r $ use formula:
$$ V = \dfrac{ 4 \cdot r^2 \cdot \pi }{ 3 }$$After substituting $ V = 320 $ we have:
$$ 320 = \dfrac{ 4 \cdot r^2 \cdot \pi }{ 3 }$$ $$ 320 \cdot 3 = 4 \cdot r^2 \cdot \pi $$ $$ 960 = 4 \cdot r^2 \cdot \pi $$ $$ r^2 \cdot \pi = \dfrac{ 960 }{ 4 } $$ $$ r^2 \cdot \pi = 240 $$ $$ r = \sqrt{ \frac{ 240 }{\pi} } $$ $$ r \approx 8.7404 $$STEP 2: find diameter $ d $
To find diameter $ d $ use formula:
$$ d = 2 \cdot r $$After substituting $ r = 8.7404 $ we have:
$$ d = 2 \cdot 8.7404 $$ $$ d \approx 17.4808 $$