Last time this problem was asked in cbse 2017 board exam. Question number 29 [i] from RS Aggarwal book page number 289, chapter volume and surface area of solid, exercise 17A.

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# A hemisphere of maximum possible diameter is placed over a cube block of side 7 cm. Find the surface area of the solid so formed.

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This answer was edited.From the figure, it can be observed that the maximum diameter possible for such hemisphere is equal to the cube’s edge, i.e., 7 cm.

Radius (r) of hemispherical part = 7/2 = 3.5 cm

Total surface area of solid = Surface area of cubical part + CSA of hemispherical part − Area of base of hemispherical part

= 6 [Edge]² + 2πr² – πr²

= 6 [Edge]² + πr²

Total surface area of solid = 6 [7]² + ( [22/7] * [ 7/2]²)

= 294 + 38.5

= 332.5 cm²

∴ Total surface area of solid 332.5 cm²