ABC26GN5046 · Volume and Surface Area
Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: · Marks: · Difficulty:
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)$257.7 \mathrm{cm}^{2}$
(b)$286 \mathrm{cm}^{2}$
(c)$292 \mathrm{cm}^{2}$
(d)$302 \mathrm{cm}^{2}$
Answer
Explanation
Internal radius, $r=4 \mathrm{cm}$; External radius, $R=5 \mathrm{cm}$. Total surface area $=2 \pi R^{2}+2 \pi r^{2}+\pi\left(R^{2}-r^{2}\right)$ $$\begin{aligned} & =3 \pi R^{2}+\pi r^{2}=[\pi(3 \times 25+16)] \mathrm{cm}^{2} . \\ & =\left(\frac{22}{7} \times 91\right) \mathrm{cm}^{2}=286 \mathrm{cm}^{2} . \end{aligned}$$
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