Cesar Millan's Dog Rue's Running Distance

To find out how many kilometers Rue has run, we need to calculate the distance he runs back and forth between the house and his master.

Since Rue runs at a constant speed of 3.0 km/h, the round trip distance he covers is twice the distance between the house and Cesar Millan.

The distance between the house and Cesar Millan is 3.0 km.

So, the round trip distance Rue covers is 2 * 3.0 km = 6.0 km.

Therefore, by the time Cesar Millan reaches home, Rue has run a total of 6.0 km.