\(h = 6r\)
\(\therefore TSA = 2\pi rh + 2\pi r^2\)
\(= 12\pi r^2 + 2\pi r^2\)
\(= 14\pi r^2\)
\(= 14 \times \frac {22}7 \times r^2 = 44r^2\)
\(\because \) Cost of painting on 1cm2 = 60 paise = ₹0.60
\(\therefore \) Cost of painting on 44r2 cm2 = ₹0.60 x 44 r2
But given that cost of painting of closed cylindrical tank = Rs 237.6
\(\therefore 44 r^2 \times 0.6 = 237.6\)
⇒ \(44r^2 = \frac{237.6}{0.6}\)
⇒ \(r^2 = \frac {237.6}{0.6} \times \frac1{44} = \frac{2376}6 \times \frac1{44} = 9\)
\(\therefore r = 3 cm\)
& \(h = 6r = 18 cm\).