For this case, the first thing we must observe is that the triangles are similar.
We can then use the following relationship:
![BC / DE = AB / (AB + BD)](https://img.qammunity.org/2019/formulas/mathematics/high-school/innqrakghfegulwe051qf0ua3kio2d71ue.png)
Clearing the value of BC we have:
![BC = (AB / (AB + BD)) * (DE)](https://img.qammunity.org/2019/formulas/mathematics/high-school/gzp0btwu3dwspa006fov0flnonzcy9lypt.png)
Substituting the values we have:
![BC = (1 / (1 + 4)) * (6)](https://img.qammunity.org/2019/formulas/mathematics/high-school/k39e3z1rojojggae2hsi1lqxl6lagnimri.png)
Rewriting we have:
Answer:
The length of BC is given by:
BC = 1.2