A practical problem states that a car travels 60 km/h and a truck travels 40 km/h. If they start from the same point and the car leaves 30 minutes before the truck, how far from the starting point will they meet?
Answer: B. 80 km
Let the time the truck travels be t hours. The car travels for t + 0.5 hours. Setting the distances equal gives 60(t + 0.5) = 40t, leading to t = 1 hour, so they meet at 80 km from the start.