10th Class Mathematics Triangles Question Bank Triangles

  • question_answer
    In the given figure, \[\angle ABC={{90}^{o}}\] and \[BD\bot AC.\] If \[BD=8cm,\]\[AD=4cm,\] then CD=

    A)  \[16\,cm\]

    B)  \[14\,cm\]       

    C)  \[15\,cm\]       

    D)         \[17\,cm\]       

    Correct Answer: A

    Solution :

                        In  \[\Delta DBA\]and\[\Delta DCB,\]we have  \[\angle BDA=\angle CDB\]    [Each \[{{90}^{o}}\]]         and \[\angle DBA=\angle DCB\]  [Each\[={{90}^{o}}-\angle A\]] \[\therefore \]  \[\Delta \,DBA\tilde{\ }\Delta DCB\]  [By AA similarity] \[\Rightarrow \]\[\frac{BD}{CD}=\frac{AD}{BD}\]\[\Rightarrow \]\[CD=\frac{B{{D}^{2}}}{AD}=\frac{8\times 8}{4}=16cm\]


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