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Question
The area of a circular ring enclosed between two concentric circles is 88 cm 2. Find the radii of the two circles, if their difference is 1 cm.
Solution
Let r cm be the radius of inner circle.
Radius of outer circle = (r+ 1) cm
Area of circular ring = Area of outer cirde - area of inner circle
⇒ π (r + 1)2 - π r1 = 88
⇒ π (r1 + 2r + 1) - π r2 = 88
⇒ π r1 + 2 π r + π - πr1 = 88
⇒ `22/7 (2"r" + 1) = 88`
⇒ 2r + 1 = `88 xx 7/22`
⇒ 2r + 1 = 28
⇒ 2r = 27
⇒ r = `27/2 = 13.5` cm
(r + 1) = 13.5 + 1 = 14.5 cm
Therefore, radii are 13.5 cm and 14.5 cm.
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