Question

. A cubical block of side 10 cm 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 sq. cm. [Use π = 3.14]

Answer 1

The largest diameter of he hemisphere = 10 cm


Surface area of solid = Surface area of the cube - area of circular part

                                     of the hemisphere + surface area of the hemisphere


                                   = 10 x 10 x 6 - 22/7 x 5² + 2 x 22/7 x 5²

                                   = 600 - 78 4/7 + 157 1/7
                         
                                   = 678 4/7 cm²

                                   = 678.57 cm²


Cost of painting = 678.57 x 5

                          = Rs. 3392.85 


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