Question

A hemi- spherical dome of a building needs to be painted. If the circumference of the base of the dome is 17.6 m, find the cost of painting it, given the cost of painting is Rs. 5 per $100c{m}^2.$

Answer 1

circumference of the base of dome (r)
$=17.6m\therefore Radius=\frac{c}{2\pi }=\frac{17.6\times 7}{2\times 22}=2.8m\therefore Surfacearea=2\pi r^2=2\times \frac{22}{7}\times (2.8{)}^2{m}^2=\frac{44}{7}\times 2.8\times 2.8m^2=49.28m^2$
Rate of painting the surface
$=Rs.5per100c{m}^2\therefore Totalcost=\frac{49.28\times 5\times 10000}{100}=Rs.24640$