X is the mid-point of the side BC of a parallelogram ABCD. DX meets AC in Y Prove that ar(ΔADY)=2ar(DYC)
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Solution
The Δ AYD and Δ XYX can be proved similar by AAA similarity criteria. Also, AD = 2 XC as X is the midpoint of BC. Hence, AY: TC = 2: 1 (As ratio is same for the similar triangles) Hence, ar(ΔADY)=2ar(DYC) = 2: 1 [Triangles on the same base and have same height have area in the ratio of bases.]