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Mayank's bird-bath is in the shape of a cylinder with a hemispherical depression at one end. The cylinder height is $1.45\,\mathrm{m}$ and the radius is $30\,\mathrm{cm}$. Taking $\pi=\frac{22}{7}$, what is the total surface area of the bird-bath? 
A$2.64\,\mathrm{m}^2$
B$3.3\,\mathrm{m}^2$
C$3.0\,\mathrm{m}^2$
D$4.2\,\mathrm{m}^2$
Answer & Solution
Correct answer: B. $3.3\,\mathrm{m}^2$
Convert $1.45\,\mathrm{m}$ to $145\,\mathrm{cm}$. Total surface area $=$ CSA of cylinder $+$ CSA of hemisphere $=2\pi rh+2\pi r^2=2\pi r(h+r)$. Substituting $r=30$ and $h=145$ gives $33000\,\mathrm{cm}^2=3.3\,\mathrm{m}^2$.
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