This distance-time graph shows the journey of an airship. Calculate the speed of the airship during the journey. Give your answer in miles per hour and if your answer is a decimal, give it to 2 d.p. 240 Distance travelled (miles) 50 60 120 180 0. 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 Time