Practice | Hashtable

1. The external and internal diameters of a hemispherical bowl are 10 cm and 8 cm respectively. What is the total surface area of the bowl ?

A. 257 cm²

B. 286 cm²

C. 292 cm²

D. 302 cm²

Solution:

Internal radius, r = 4 cm
External radius, R = 5 cm
Total surface area :

\begin{aligned} = 2 π R^{2} + 2 π r^{2} + π (R^{2} - r^{2}) \\ = 3 π R^{2} + π r^{2} \\ = [π (3 \times 25 + 16)] c m^{2} \\ = (\frac{22}{7} \times 91) c m^{2} \\ = 286 c m^{2} \end{aligned}

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