A plane maintains an average speed of 225mph from London to New York. It then returns from New York to London at an average speed of 180mph. What is the average speed for the entire journey?




200mph: if the one-way distance was 1000 miles (for example), the outward journey took 1000/225 hours and the return journey took 1000/180 hours. Therefore the total time taken was (1000/225 + 1000/180) hours for 2000 miles. So the average speed was 2000 / (1000/225 + 1000/180) which equals 200mph. The answer remains the same if you change the distance to any number of miles.