You should know the difference between the displacement and the distance. The distance is the length traveled all throughout the path covered. The displacement is the length traveled from the starting point to the final point. In this case, the distance is
Distance = 11 km + 11 km = 22 km
In the diagram, the red line is the path for the displacement. By pythagorean theorem, the solution is
Displacement = √11² + 11² = 15.56 km
