8
The problem involves a triangle ABC where a line segment DE is drawn parallel to BC, intersecting sides AB and AC at points D and E, respectively. We are given the lengths AD = 3, DB = 6, and AE = 4, and we need to find the length of EC.
When a line is drawn parallel to one side of a triangle intersecting the other two sides, it divides the two sides proportionally. This is known as the Basic Proportionality Theorem (BPT) or Thales's Theorem.
According to the BPT, for triangle ABC with DE || BC:
$ \frac{AD}{DB} = \frac{AE}{EC} $
$ \frac{3}{6} = \frac{4}{EC} $
$ \frac{1}{2} = \frac{4}{EC} $
$ 1 \times EC = 2 \times 4 $
$ EC = 8 $
Therefore, the length of EC is 8.
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