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Question
A sphere is cut into two equal halves and both the halves are painted from all the sides. The radius of the sphere is r units and the rate of painting is Rs 8 per sq. unit. What is the total cost of painting the two halves of the sphere in rupees?
A sphere is cut into two equal halves and both the halves are painted from all the sides. The radius of the sphere is r units and the rate of painting is Rs 8 per sq. unit. What is the total cost of painting the two halves of the sphere in rupees?
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Solution
The correct option is C 48πr2
Curved surface area of the sphere = 4πr2
Flat surface areas of two hemispheres = 2 x πr2
Total surface area = 6πr2
Therefore, total cost = Rs 8 x 6πr2
= Rs 48 πr2
Curved surface area of the sphere = 4πr2
Flat surface areas of two hemispheres = 2 x πr2
Total surface area = 6πr2
Therefore, total cost = Rs 8 x 6πr2
= Rs 48 πr2
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