The perimeter of a semi-circular area is 18cm, then the

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The perimeter of a semi-circular area is 18cm, then the radius is :
(using π = 22/7)

Using Rule 14,
Perimeter of semi-circular region = 18 cm
∴ πr + 2r = 18
⇒ r (π + 2) = 18

⇒ r		22	+ 2		= 18
		7

⇒ r		36		= 18
		7

⇒ r =	18 × 7	=	7	= 3	1	cm
	36		2		2