Question

please explain this question with figure​

Answer 1

Answer:

Answer:

The radius of the inner circle is 14cm.

Step-by-step explanation:

Let the radius of the inner circle = r

Given :

Area enclosed between two concentric circles, A = 770 cm ^ 2

Radius of the outer circle, R = 21cm

Area enclosed between two concentric circles, A = Area of the Outer circle - Area of the inner circle

770 = Pi * R ^ 2 - Pi * r ^ 2

77O = Pi(R ^ 2 - r ^ 2)

770 = Pi(21 ^ 2 - r ^ 2)

770 = Pi(441 - r ^ 2)

770 = 22/7 * (441 - r ^ 2)

770 * 7 = 22(441 - r ^ 2)

(441 - r ^ 2) = 770 * 7 / 22

(441 - r ^ 2) = (70 * 7) / 2

(441 - r ^ 2) = 35 * 7

245 = 441 - r ^ 2

r ^ 2 = 441 - 245

r ^ 2 = 196

r = √196

r = 14

r = 14cm

Hence, the radius of the inner circl is 14cm.

HOPE THIS ANSWER WILL HELP YOU....

Answer 2

Answer:

r = 14 cm

Step-by-step explanation:

Radius of outer circle (R) = 21 cm

Let the radius of inner circle be = r cm

Area enclosed between concentric circle = 770²

$\pi \: R² \: - \pi \: {r}^{2} = 770 \\ \frac{22}{7} \times 21 \times 21 \ \times {r}^{2} = 770 \\ \frac{22}{7} (441 - r {}^{2} ) = 770 \\ 441 - {r}^{2} = \frac{770 \times 7}{2} \\ 441 - {r}^{2} = 245 \\ {r}^{2} = 441 - 245 \\ {r }^{2} = 196 \\ r = \sqrt{196} = 14 \\ 14cm$

Therefore, the radius of inner circle is = 14 cm.

Hope it helps!

Please also refer the above attachment.