Average speed = Total distance ÷ Total time.<br><br>&bull; Time to go: 120 ÷ 60 = 2 h.<br>&bull; Time to return: 120 ÷ 40 = 3 h.<br>&bull; Total distance = 120 + 120 = 240 km.<br>&bull; Total time = 2 + 3 = 5 h.<br>&bull; Average speed = 240 ÷ 5 = 48 km/h.<br><br>Final Answer: 48 km/h