A wooden bowl is in shape of a hollow hemisphere of internal radius 7 cm and thickness 1 cm. What is the total surface area (in sq.cm) of the bowl? (Take: π = 22/7)

The hemispherical bowl has three surfaces to calculate : the interior hemisphere $$(r_{int} = 7)$$ cm , the exterior hemisphere $$(r_{ext} = 7+1 = 8)$$ 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

= $$[2 \pi (7)^2] + [2 \pi (8)^2] + [\pi (8^2 - 7^2)]$$

= $$\pi (98 + 128 + 64 - 49) = 241 \pi$$

= $$241 \times \frac{22}{7} = 757.43 cm^2$$