A wooden bowl is in shape of a hollow hemisphere of internal radius 9 cm and thickness 1 cm. Find the total surface area of the bowl? ?->(Show Answer!)

1. A wooden bowl is in shape of a hollow hemisphere of internal radius 9 cm and thickness 1 cm. Find the total surface area of the bowl?

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By: anil on 05 May 2019 02.15 am

The hemispherical bowl has three surfaces to calculate : the interior hemisphere $$(r_{int} = 9)$$ cm , the exterior hemisphere $$(r_{ext} = 9+1 = 10)$$ cm and the annular(ring shaped) top edge $$(r_{ext} , r_{int})$$ Area of hemisphere = $$2 pi r^2$$ and area of annular = $$pi (r^2_{ext} - r^2{int})$$ Total surface area of hemisphere is the sum of these 3 areas = $$[2 pi (9)^2] + [2 pi (10)^2] + [pi (10^2 - 9^2)]$$ = $$pi [(2 imes81) + (2 imes100) + (100 - 81)]$$ = $$pi(162 + 200 + 19) = 381 pi$$ = $$381 imes frac{22}{7} = 1197.42$$ $$cm^2$$ => Ans - (D)

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