Joe, a superhero, finishes a meal at a restaurant only to find he's left is wallet at home. Not wanting to reveal his secret identity to his date, he excuses himself and slips outside. Dashing home at 170 mph, he snatches his wallet from his nightstand and races back to the restaurant at 290 mph. Discounting the time it took to find his wallet, what was his average speed for the trip?

Joes average speed is ____ miles per hour.

(Round to one decimal place as needed.)