A) \[=28\times \frac{66}{7}=264\,\,\text{m}\]
B) \[550\,\,\text{c}{{\text{m}}^{2}}\]
C) \[565\,\,\text{c}{{\text{m}}^{2}}\]
D) \[675\,\,\text{c}{{\text{m}}^{2}}\]
Correct Answer: B
Solution :
| Radius outer circle (R) = 20 cm |
| Radius inner circle (r) = 15 cm |
 |
| \[\therefore \] Area of the ring |
| = [Area of outer circle \[-\]Area of inner circle] |
| \[=(\pi {{R}^{2}}-\pi {{r}^{2}})=\pi ({{R}^{2}}-{{r}^{2}})\] |
| \[=\frac{22}{7}({{20}^{2}}-{{15}^{2}})\] |
| \[=\frac{22}{7}(20+15)(20-15)\] |
| \[=\frac{22}{7}\times 35\times 5=550\,\,\text{c}{{\text{m}}^{2}}\] |
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