A) \[9\pi \,{{m}^{2}}\]
B) \[16\pi \,{{m}^{2}}\]
C) \[20\pi \,{{m}^{2}}\]
D) \[36\pi \,{{m}^{2}}\]
Correct Answer: C
Solution :
| [c] Let \[{{d}_{1}}\] and \[{{d}_{2}}\] be external and internal diameters. |
| Area of the circular path \[=\pi \left[ {{\left( \frac{{{d}_{1}}}{2} \right)}^{2}}-{{\left( \frac{{{d}_{2}}}{2} \right)}^{2}} \right]\] |
| \[=\pi \left[ {{\left( \frac{12}{2} \right)}^{2}}-{{\left( \frac{8}{2} \right)}^{2}} \right]=\pi \{36-16\}=20\pi {{m}^{2}}\] |
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