Question

the radius of an outer circle is 21 cm and the inner circle is 14 cm find the area of circular ring​

Answer 1

Answer:

$area \: of \: outer \: circle \: = \pi {r}^{2} \\ \frac{22}{7} \times 21 \times 21 \\ = 22 \times 3 \times 21 \\ = 1386 = \beta \\ \\ area \: of \: inner \: circle \: = \pi {r}^{2} \\ \\ \frac{22}{7} \times 14 \times 14 \\ = 22 \times 2 \times 14 \\ = 616 = \alpha \\ \\ \\ area \: of \: circular \: ring \: = \beta - \alpha \\ 1386 - 616 \\ = 770$

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