Average Speed = Total Distance ÷ Total Time.
• Total distance = 45 km × 2 = 90 km (to and from)
• Total time = \( \frac{3}{4} + \frac{1}{2} = \frac{3}{4} + \frac{2}{4} = \frac{5}{4} \) h = 1.25 h
• Average speed = 90 km ÷ 1.25 h = 72 km/h
Final Answer: 72 km/h