In ΔABC, it is given that DE || BC. If AD = 3 cm, DB = 2 cm and DE = 6 cm, then BC = ?
In ΔADE and ΔABC
∠ADE = ∠ABC [Corresponding angles as DE || BC]
∠AED = ∠ACB [Corresponding angles as DE || BC]
ΔADE ~ ΔABC [By Angle-Angle Similarity criterion]
[Corresponding sides of similar triangles are in the same ratio]
Now,
Given, AD = 3 cm
DB = 2 cm
DE = 6 cm
⇒ AB = AD + DB = 3 + 2 = 5 cm
Using this in above equation,
⇒ BC = 10 cm