Page 3 - IX Lesson Note- 3 Ttriangles having equal- ch 9 Area of Parallelograms and Triangles
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•  Example :1


               Prove that a median of a triangle divides it into two triangles of equal area.













               Given: A  ABC and AD is a median.
               To Prove: ar( ABD) = ar( ADC)
               Construction: Let AP BC.


               Proof: ar( ABD)


               ar( ADC)
               Since, AD is the median therefore, BD = DC   (iii)
               From (i), (ii) and (iii), we get,
               ar( ABD) = ar( ADC).

               EXAMPLE 2
               The cross-section of a canal is a trapezium in shape. If the canal is 8 m wide at the
               top and 10 m wide at the bottom and the area of cross-section is 72 sq. m, determine
               its depth.


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