9th Class Mathematics Quadrilaterals Question Bank Quadrilaterals

  • question_answer
    In a\[\Delta ABC,P,Q\]and R are the mid-points of sides BC, CA and AB respectively. If AC =21 cm, BC=29cmandAB=30cm.The perimeter of the quadrilateral ARPQ \ is _____.     

    A)  91 cm                         

    B)         60 cm             

    C)                     51 cm            

    D)         70cm                                                              

    Correct Answer: C

    Solution :

    Given, AC = 21 cm, AB = 30 cm \[\because \]Q is mid-point of AC \[\therefore \]\[AQ=\frac{AC}{2}=\frac{21}{2}cm\]                      ?(i) \[\because \]R is mid-point of AB \[AR=\frac{AB}{2}=\frac{30}{2}cm\]                ?(ii) In\[\Delta BCA,\] P is mid-point of BC, R is mid-point of Ba then, by mid-point theorem, \[PR||AC\]and \[PR=\frac{1}{2}AC=\frac{21}{2}\]         ?(iii) Similarly, Q is mid-point of AC, P is mid-point of BC, then \[QP||AB\]and \[QP=\frac{1}{2}AB=\frac{30}{2}\]                              ?.(iv) \[\therefore \]Perimeter of quad. ARPQ \[=AR+RP+PQ+AQ\] \[=\frac{30}{2}+\frac{21}{2}+\frac{30}{2}+\frac{21}{2}\](from (i), (ii), (iii) and (iv)) \[=2.\frac{30}{2}+2.\frac{21}{2}=30+21=51\,cm.\]


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