Question

the interior of a building is in the form of right circular cylinder of radius 7m and height 6m , surrounded by a right circular cone of vertical angle 60 degree . Find the cost of painting the building from inside at the rate of 30 / m

Answer 1

We have r= 7m and h=6m
Surface area of building wall= 2πr.h=7*6*22/7= 132 m²
As the vertical angle is 60 degree we have slant height= dia
                                                                       s= 2r= 14
lateral surface area of cone= πrs=22*7*14/7=308 m²
Total surface area = 132+308= 440m²
Painting rate is Rs 30/m²
Total cost of painting= 440*30= Rs13200