Question

In triangle ABC, it is given that DE is parallel to BC.

If AD=3cm, DB= 2cm, and DE=6cm, then find BC?​

Answer 1

Given: ABC is a triangle , DE parallel BC and AD= 3 cm, DB=2 cm and DE=6 cm

To find: AE

sol: Since DE parallel BC

angle ADE= angle ABC (corresponding angles)

and angle AED = angle ACB

Triangle ADE ≈ triangle ABC ( by AA similarity)

therefore , AD/AB=DE/BC=AE/AC (1)

From (1)

AD/AB=AE/AC

2/5=x/18

2×18=5x

36=5x

x=36/5

x=7.5cm

∵ AE = 7.5 cm

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