Question

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

Answer 1

let radii be r and R..so according to the question...R-r=7cm..so R=7+r...so..area enclosed by circular rings=π(R^2-r^2)=286=>22/7(R+r)(R-r)=286=>22/7*(7+r+r)(7)=>286=22*(7+2r)=>286/22=7+2r=>13-7=2r=>6/2=r=3cm= r...so R=7+3=10cm(ans)