Question

The inner curved surface area of a hemispherical dome of a building needs to be painted. If the circumference of the base is $17.6m$, find the cost of painting it at the rate of Rs.$5$ per sq.m

• A. Rs.$246.40$
• B. Rs.$24.40$
• C. Rs.$26.40$
• D. None of these

Answer 1

The correct option is A Rs.$246.40$

We have,

Circumference $=17.6m$

Circumference of circle $=2\pi r$

$17.6=2\times \frac{22}{7}\times r$

$44r=17.6\times 7$

$r=\frac{123.2}{44}=2.8m$

Now, Curved surface area of the hemisphere $=2\pi r^2$

$=2\times \frac{22}{7}\times 2.8\times 2.8$

$49.28m^2$

Cost of painting $=Rs.5per{m}^2$

Total cost of painting $=49.28\times 5$

$=Rs.246.4$

Hence, the cost of painting is $=Rs.246.4$