Question 977266
The internal and external diameters of a hollow sphere are 20cm and 28cm respectively find the cost of painting all over the hollow hemisphere at 14paise per square cm 
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{{{SA = pi*d^2}}}
There are 2 surfaces, the inside and the outside
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Total SA = {{{pi*20^2 + pi*28^2}}} sq cms for a sphere
The hemisphere's SA ia 1/2 that.
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Multiply the cost/sq cm by the SA