If a circle of radius 12 cm is divided into two equal parts

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If a circle of radius 12 cm is divided into two equal parts by one concentric circle, then radius of inner circle is :

1. 6 cm
2. 4 cm
3. 6√2 cm
4. 4√2 cm

Correct Option: C

According to the question,
π × 12² = 2πr²
⇒ 2r² = 12 × 12

⇒ r² =	12 × 12	= 72
	2

⇒ r = √72 = 6√2 cm.