Question

Dave is walking from the back of a train to the front of the train at a rate of 6

kilometers per hour (km/hr). The train is traveling at a rate of 42 km/hr. What is
Dave's speed, relative to the ground?

Answer 1

48 km/hr. Because the trains speed remains constant and is unaffected to Dave’s speed and Dave’s speed will remain relative to the trains speed. Taken that, when Dave is moving 0 km/hr he is moving at 42km/hr. So his speed must only add to that.