Question

A cylindrical vessel open at the top has diameter 20cm and height 14cm. Find the cost of the tin- plating it on the inside at the rate of 50 paise per hundred square centimetre.

Answer 1

Diametre of the vessel= 20 cm

$\therefore$ Radius(r) $=\frac{20}{2}$ = 10cm
and height (h) =14cm
$\therefore$ Surface area of its inner part
$=2\pi rh+\pi r^2=\pi r(2h+r)$
$=\frac{22}{7}\times 10(2\times 14+10)c{m}^2$
$=\frac{220}{7}\times 38=\frac{8360}{7}c{m}^2$
Rate of tin-plating = 50 paise per $100c{m}^2$
$\therefore$ Total cost $=\frac{8360}{7}\times \frac{50}{100\times 100}$
=5.97