Question

solve it by solution

Answer 1

Let the radius of the inner circle be X and the value of PI=22/7 . Area enclosed between the concentric circles=
$\frac{22}{7} ( {21}^{2} - {x}^{2} ) = 770$
=>
$441 - {x}^{2} = 770 \times \frac{7}{22}$
=>
$441 - {x}^{2} = 245 = > {x}^{2} = 441 - 245$
=>
${x}^{2} = 196 = > x = 14$
So the radius of the inner circle is 14 centimetres. Hope it helps you and Mark me as Brainliest.

Answer 2

Answer:

14 cm

Step-by-step explanation:

Radius of outer circle R = 21 cm.

Radius of inner circle r = r cm.

Area of shaded portion = 770 cm^2.

⇒ π(R² - r²) = 770

⇒ (22/7)(21² - r²) = 770

⇒ 441 - r² = 770 * 7/22

⇒ 441 - r² = 35 * 7

⇒ 441 - r² = 245

⇒ -r² = 245 - 441

⇒ -r² = -196

⇒ r = √196

⇒ r = 14 cm.

Radius of inner circle = 14 cm.

Hope it helps you.

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