Question

A solid is composed of a cylinder with hemispherical ends. If the whole length of the solid is 104cm and radius of each of hemispherical ends is 7cm. find the cost of polishing its surface at the rate of  Rs 10 per dm² ?

Answer 1

Given radius of hemispherical ends = 7cm

Height of body (h+2r)= 104cm 

Curved surface area of cylinder = 2πrh

Substitute ‘h’ value in (1)

Curved surface area of cylinder =  2π(7)(90)

=3948.40cm²    ................(2)

Curved surface area of 2 hemisphere = 2(2πr²)

Total curved surface area = (2) + (3)