Question

The water for a factory is stored in a hemispherical tank, open at top, whose internal radius is 7 m. Find the interior surface area that needs to be painted.

• A. 208 m${}^2$
• B. 358 m${}^2$
• C. 218 m${}^2$
• D. 308 m${}^2$

Answer 1

The correct option is D 308 m${}^2$

Given, tank is in the shape of hemisphere and irs radius is 7 m.
And cuved surface of hemisphere of radius 'r' = $2\pi r^2$

$\therefore$ Area of the surface that needs to be painted
$=2\pi r^2=2\times \frac{22}{7}\times (7{)}^2=2\times 22\times 7=308m^2$