How many millimeters are in 0.05 kilometers?

First answer these questions:

How many millimeters in a meter?
How many meters in a kilometer?

0.5 km\,\times\, \frac {m}{km}\,\times\, \frac {mm}{m} \,=\, X \, mm

You can also use Google

Let me google that for you (http://www.lmgtfy.com/?q=Convert+kilometers+to+millimeters)