Two circles which are not congruent touch externally. The sum of their areas is 130πcm2 and the distance between their centres is 14cm. The sum of radii of the circles is
A
14cm
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B
21cm
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C
7cm
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D
28cm
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Solution
The correct option is A14cm Given−P&Qarethecetresoftwocirclesofradiusr1&r2respectively,touchingeachotheratM.PQ=14cm.Tofindout−thesumoftheirradii=?Solution−WedrawthecommontangentABatM.i.ePM=r1&QM=r2.Now∠AMP=90obecauseifalinetouchesacircleatapointthentheradiusthroughthatpointisperpendiculartothetangentatthatpoint.Similarly∠AMQ=90o.So∠AMP+∠AMQ=90o+90o=180o.∴∠AMP&∠AMQarelinearpair.SoPM&QMareonthesamestraightline.∴ThedistancebetweenthecentresP&QisPQ=PM+QM=r1+r2.ButPQ=14cm(given).∴r1+r2=14cm.Ans−OptionA.