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.
Let r cm be the radius and h cm be the height of the cylinder then,
r = 30 cm,
h = 1.45 m = 145 cm.
Lei r1 cm be the radius of the hemisphere, then
r1 = 30 cm
Now,
The Total Surface Area of the bird bath
= C.S.A of cylinder + C.S.A of Hemisphere
= 2 rh + 2 r1 2
= 2rh + 2r2 [∵ r = r1]
= [2 ∵ r (h + r)] cm2
= 33000 cm2
= 3.3 m2
(Use π = 3.14).