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  • The area of a circular ring enclosed between two concentric circles is 286 cm^2. Find the radii of the two circles,given that their difference is 7 cm.

The area of a circular ring enclosed between two concentric circles is 286 cm^2. Find the radii of the two circles,given that their difference is 7 cm.

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Let the radii of the outer and inner circles be R cm and r cm respectively.

According to the given Info,
R-r=7    ...(i)
and π(R2-r2)=286
Rightarrow π(R-r)(R+r)=286
Rightarrowfrac227 imes7 imes(R+r)=286        [using(i)]
RightarrowR+r=13       ...(ii)
Adding (i) and (ii),we get
2R=20 Rightarrow R=10
Subtracting (i) and (ii),we get
2r=6 Rightarrow r=3
herefore The radii of the two circles are 10 cm and 3 cm.

Posted by

Deependra Verma

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