Question

BC¯¯¯¯¯ is parallel to DE¯¯¯¯¯. What is AB?

Answer 1

`AB=34`

Explanation:

Given `BC` is parallel to `DE` :

Construct line segment `BF` parallel to `CE`,
`=> BF=CE=21`, as shown in the diagram.

`=> DeltaBDF, DeltaABC and DeltaADE` are similar.
`=> (AB)/(AC)=(BD)/(BF)`
`=> (AB)/42=17/21`
`=> AB=(42xx17)/21=34`