Question: If 64 identical small spheres are made out of a big sphere of diameter 8 cm, what is surface area of each small sphere?
Options:
A) $ \pi cm^{2} $
B) $ 2\pi cm^{2} $
C) $ 4\pi cm^{2} $
D) $ 8\pi cm^{2} $
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Answer:
Correct Answer: C
Solution:
- Volume of small spheres
$ =\frac{Volumeofbiggersphere}{Numberofsmallsphere}=\frac{\frac{4}{3}\pi {{(4)}^{3}}}{64} $
$ =\frac{4}{3}\times \frac{\pi \times 4\times 4\times 4}{64}=\frac{4}{3}\pi cm^{2} $
Let radius of small sphere be r'.
$ \therefore $ $ \frac{4}{3}\pi r^{3}=\frac{4}{3}\pi $
$ \Rightarrow $ $ r’=1cm $
Now, surface area of small sphere $ =4\pi r{{’}^{2}}=4\pi cm^{2} $