A cubical block of side 10cm is surmounted by a hemisphere.What is the largest diameter that the hemisphere can have?Find the cost of painting the total surface area of the solid so formed,at the rate of rs. 5 per 100 sq cm.
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Total surface area of the solid = Total surface area of the cube + curved surface area of the hemisphere - Area of the base of the hemisphere
= 6a2 + 2πr2 -πr2
= [ 6 x (10)2 + 2 x 3.14 x (5)2 - 3.14 x (5)2] cm2
= (600 +157 -78.5 ) cm2
= 678.5 cm2
Cost of painting = Rs 5 per 100 cm2
Therefore,
Cost of painting the solid = 678.5 x (5/100) = Rs. 33.90
Hence, the approximate cost of painting the solid so formed is Rs. 33.90
= 6a2 + 2πr2 -πr2
= [ 6 x (10)2 + 2 x 3.14 x (5)2 - 3.14 x (5)2] cm2
= (600 +157 -78.5 ) cm2
= 678.5 cm2
Cost of painting = Rs 5 per 100 cm2
Therefore,
Cost of painting the solid = 678.5 x (5/100) = Rs. 33.90
Hence, the approximate cost of painting the solid so formed is Rs. 33.90
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