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 the side (edge) of the cube be a cm, then a
= 5 cm.
Let radius of the hemisphere be r, then
r = 2.1 cm
Now,
The total surface area of the block
= T.S.A of cube - base area of hemisphere + C.S.A of hemisphere
= 6 (side)2 – r2 + 2r2
= 150 – r2 + 2 r2
= 150 + 2
(Use π = 3.14).