In triangle ABC, D is on AB and E is on AC with DE parallel to BC. $AD = 4$ cm, $DB = 6$ cm and $AE = 5$ cm. What is EC?

Explanation

1. 01

   By the basic proportionality theorem, $AD : DB = AE : EC$.

2. 02

   $\frac{4}{6} = \frac{5}{EC}$, so $EC = \frac{5 \times 6}{4} = 7.5$ cm.