The decorative block shown in fig. is made of two solids - a cube and a hemisphere. The base of the block is a cube with edge 5 cm, and the hemisphere fixed on the top has a diameter of 4.2 cm. Find the total surface area of the block.
We have,
r = radius of the cylinder
= radius of hemispherical ends = 14 cm
h = height of cylinder = 72 cm
∴ Total surface area = curved surface area of the cylinder + surface areas of hemispherical ends
= (2rh +2 x 2r2) cm2
= 2r (h + 2r) cm2
Now, cost of polishing the surface of the solid at the rate of 5 paise per sq. m
(Use π = 3.14).