SSC Quantitative Aptitude Geometry Question Bank Triangles and Their Properties (II)

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

    A) \[80{}^\circ ,\]\[60{}^\circ ,\]\[40{}^\circ \]

    B) \[70{}^\circ ,\]\[50{}^\circ ,\]\[60{}^\circ \]

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

    D) \[80{}^\circ ,\]\[55{}^\circ ,\]\[45{}^\circ \]

    Correct Answer: C

    Solution :

    [c] Let \[\angle C=x\] Then, \[\angle B=30{}^\circ +\angle C=30{}^\circ +x\] and \[\angle A=15{}^\circ +\angle B=45{}^\circ +x\] Now, \[\angle A+B+\angle C=180{}^\circ \] \[\Rightarrow \]   \[45{}^\circ +x+30{}^\circ +x+x=180{}^\circ \] \[\Rightarrow \]   \[75{}^\circ +3x=180{}^\circ \]\[\Rightarrow \]\[3x=105{}^\circ \] \[\Rightarrow \]   \[x=35{}^\circ \] \[\therefore \]      \[\angle A=45{}^\circ +x{}^\circ =45{}^\circ +35{}^\circ =80{}^\circ \] \[\angle B=30{}^\circ +x{}^\circ =30{}^\circ +35{}^\circ =65{}^\circ \] \[\angle C=x{}^\circ =35{}^\circ \]


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