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9th Class Mathematics Lines and Angles Question Bank Lines and Angles

  • question_answer
    \[A,\,\,B\] and \[C\] are the three angles of a triangle. If \[A-B={{15}^{o}}\] and\[B-C={{30}^{o}}\], find \[\angle A,\,\,\angle B\] and\[\angle C\].

    A) \[{{80}^{o}},\,\,{{65}^{o}},\,\,{{35}^{o}}\]            

    B) \[{{65}^{o}},\,\,{{80}^{o}},\,\,{{35}^{o}}\]

    C)        \[{{35}^{o}},\,\,{{80}^{o}},\,\,{{65}^{o}}\]

    D)        \[{{80}^{o}},\,\,{{35}^{o}},\,\,{{65}^{o}}\]

    Correct Answer: A

    Solution :

    \[A+B+C={{180}^{o}}\] \[\Rightarrow \]\[({{15}^{o}}+B)+B+(B-{{30}^{o}})={{180}^{o}}\] \[\Rightarrow \]\[A={{80}^{o}},C={{35}^{o}}\]


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