A girl, a boy, and a dog start walking down a road. They start at the same time, from the same point, in the same direction. The boy walks at 5 km/h, the girl at 6 km/h. The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn. How far does the dog travel in 1 hour?

The dog runs at a constant speed of 10 km/h for 1 hour. Distance = speed × time. The dog travels 10 km/h × 1 h = 10 km. The movements of the boy (5 km/h) and girl (6 km/h) are irrelevant to the dog's total distance since the dog's speed is constant and the time is given. Options A (5km) and B (6km) are the boy's and girl's speeds respectively, not the dog's distance.