A cylindrical vessel, without lid, has to be tin-coated on its both sides. If the radius of the base is 70 cm
Question:

A cylindrical vessel, without lid, has to be tin-coated on its both sides. If the radius of the base is $70 \mathrm{~cm}$ and its height is $1.4 \mathrm{~m}$, calculate the cost of tin-coating at the rate of Rs $3.50$ per $1000 \mathrm{~cm}$.

Solution:

Given that

Radius of the vessel (r) = 70 cm

Height of the vessel (h) = 1.4 m = 140 cm

The area to be tin coated

$=2 *\left(2 \pi r h+\pi r^{2}\right)$

= 2πr (2h + r)

= 2 * 3.14 * 70[(2 * 140) + 70]

$=154000 \mathrm{~cm}^{2}$

Required cost $=\frac{154000 * 3.5}{1000}=$ Rs 539