9th Class Mathematics Areas of Parallelograms and Triangles Question Bank Areas of Parallelograms and Triangles

  • question_answer
    ABCD is parallelogram, G is the point on AB such that AG = 2GB, E is point on DC such that CE = 2DE and F is the point on BC such that BF = 2FC. Then, match the following:
      Column-I   Column-II
    p \[ar(ADEG)\] (i) \[\frac{1}{6}ar(ABCD)\]
    Q \[ar(\Delta EGB)\] (ii) \[ar(GBCE)\]
    R \[ar(\Delta EFC)\] (iii) \[ar(\Delta GBCE)\]
    S \[ar(\Delta EFC)\] (iv) \[\frac{1}{2}ar(\Delta EBF)\]
               

    A)
    P-i Q-ii R-iii S-iv
                   

    B)       
    P-iii Q-i R-iv S-ii
                   

    C)       
    P-iii Q-ii R-iv S-i
                   

    D)
    P-ii Q-i R-iii S-iv

    Correct Answer: B

    Solution :

              We have, ABCD is a parallelogram, AG = 2 GB, CE = 2 DE and BF = 2 FC. Let AL be the height of ABCD. (P) \[ar(ADEG)=\frac{1}{2}(AG+DE)AL\] [\[\because \]ADEG is a trapezium] \[=\frac{1}{2}\left[ \frac{2}{3}AB+\frac{1}{3}CD \right]AL\] \[\frac{1}{2}\left[ \frac{2}{3}CD+\frac{1}{3}AB \right]AL\] [\[\because \]ABCD is a parallelogram] \[=\frac{1}{2}[CE+GB]AL=ar(CEGB)\] (Q) \[\therefore \]Since, \[AG=2\,GB.\](given) AB = AG + GB = GB +GB = 3GB \[\Rightarrow \]\[GB=\frac{1}{3}AB\] \[\therefore \]\[ar(\Delta \Epsilon G\Beta )=\frac{1}{2}(GB)(AL)=\frac{1}{2}\left[ \frac{1}{3}AB.AL \right]\] \[=\frac{1}{6}ar(ABCD)\] (r) \[\therefore \]Since, BF = 2 FC BC = BF + FC = 2 FC +FC = 3 FC  \[\Rightarrow \]\[FC=\frac{1}{3}BC\] \[\therefore \]\[ar(\Delta \Epsilon FC)=\frac{1}{2}(CF)\times height\] \[=\frac{1}{2}\left( \frac{1}{3}BC\times height \right)\] \[=\frac{1}{2}\left[ \frac{1}{2}\left( \frac{2}{3} \right)BC\times height \right]\] \[=\frac{1}{2}\left[ \frac{1}{2}BF\times height \right]=\frac{1}{2}[ar\,\Delta \Epsilon \Beta F]\] (s) \[\therefore \]\[ar(\Delta EGB)=\frac{1}{2}\times BG\times AL\] \[=\frac{1}{2}\left[ \frac{1}{3}AB\times AL \right]\]          \[\left[ \left( \because BG=\frac{AB}{3} \right) \right]\] \[=\frac{1}{2}\left[ \frac{1}{3}CD\times AL \right]\] [\[\because \]ABCD is a parallelogram] \[=\frac{1}{2}\left[ \frac{1}{3}\times 3DE\times h \right]\]             \[(\because \,CD=3DE)\] \[=\frac{1}{2}\left[ DE\times h \right]=ar(\Delta \Epsilon DG)\]


You need to login to perform this action.
You will be redirected in 3 sec spinner