A horse gallops a distance of 60 meters in 15 seconds. Then, he stops to eat some grass for 20 seconds. Next, he trots for 25 seconds over 60 meters. (The horse trots in the same direction he galloped.) Finally, the horse races home (back to its starting position), traveling 120 meters in 20 seconds. Graph the horse's movements on the following position-time chart. Calculate the horse’s average speed for the entire journey. i don't really understand how to calculate the average speed any one know how