A hollow spherical shell is made of a metal of density 7\text{ g/cm}^{3}. If its internal and external radii are 3 cm and 6 cm respectively, then what is the mass of the shell? (take \pi=\frac{22}{7})

Explanation

Volume of metal in the hollow shell = \frac{4}{3}\pi (R^3 - r^3) = \frac{4}{3} \times \frac{22}{7} \times (6^3 - 3^3) = \frac{88}{21} \times (216 - 27) = \frac{88}{21} \times 189 = 88 \times 9 = 792\text{ cm}^3. Mass = \text{Volume} \times \text{Density} = 792 \times 7 = 5544\text{ g}.

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