Given:
Consider [tex]AB\parallel DE[/tex] in triangle ABC and [tex]AD=8,DC=3.2,BE=9[/tex].
To find:
The length of BC.
Solution:
Basic proportionality theorem (BPT): If a line intersect the two sides of triangle and parallel to the third side, then that line intersects the other two sides proportionally.
Using Basic proportionality theorem, we get
[tex]\dfrac{AD}{DC}=\dfrac{BE}{EC}[/tex]
[tex]\dfrac{8}{3.2}=\dfrac{9}{EC}[/tex]
On cross multiplication, we get
[tex]8\times EC=9\times 3.2[/tex]
[tex]EC=\dfrac{28.8}{8}[/tex]
[tex]EC=3.6[/tex]
Now,
[tex]BC=BE+EC[/tex]
[tex]BC=9+3.6[/tex]
[tex]BC=12.6[/tex]
Therefore, the length of side BC is 12.6 units.
