To find radius $ r $ use formula:
$$ V = \dfrac{ r ^{ 2 } \cdot h \cdot \pi}{ 3 } $$After substituting $ V = 175 $ and $ h = 211 $ we have:
$$ 175 = \dfrac{ r ^{ 2 } \cdot 211 \cdot \pi}{ 3 } $$$$ 175 \cdot 3 = r ^{ 2 } \cdot 211 \cdot \pi $$$$ 525 = 211 \cdot r ^{ 2 } \cdot \pi $$$$ r ^{ 2 } = \dfrac{ 525}{ 211 \, \pi } $$$$ r ^{ 2 } = 167.1128 $$$$ r = \sqrt{ 167.1128 } $$$$ r = 12.9272 $$