Q. 293.6( 16 Votes )

# A cubical block o

Answer :

Length of side of cubical block = a = 10 cm

Since, a cubical block is surmounted by a hemisphere, so, the largest diameter of hemisphere = 10 cm

Since, hemisphere will be touching the sides of cubical block.

Radius of hemisphere = r = Diameter ÷ 2 = 10/2 cm = 5 cm

Surface area of solid = Surface area of cube – Area of circular part of hemisphere + Curved surface area of hemisphere

Total Surface area of solid = 6a^{2} – πr^{2} + 2πr^{2} = 6a^{2} + πr^{2}

= 6 × 10 × 10 cm^{2} + 3.14 × 5 × 5 cm^{2}

= 678.5 cm^{2}

Rate of painting = Rs 5/100 cm^{2}

Cost of painting the total surface area of the solid so formed = Total Surface area of solid × Rate of painting

Cost of painting the total surface area of the solid = Rs 5/100 × 678.5

= Rs 33.925

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