Question extracted from RD sharma of class 10th, Chapter no. 4

Chapter name:- Triangles

Exercise :- 4.2

This is very basic and important questions. And has been asked in several times in exams

In this question we have ΔABC, in which D and E are points on the sides AB and AC respectively such that DE || BC.

Also it is given that AD/BD = 4/5 and EC = 2.5 cm,

Now we have to Find AE.

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Given:Length of side AD/BD = 4/5 and EC = 2.5 cm

To find: Length of side AC.By using Thales Theorem, we get

AD/BD = AE/CE – equation 1

Now, putting values in equation 1,

Then, 4/5 = AE/2.5

∴ AE = 4 × 2.55 = 2 cm

Therefore, Length of side AE is 2 cm