Trucks (10 m long) and cars (5 m long) go on a single lane bridge. There must be a gap of at least 20 m after each truck...

Question

Trucks (10 m long) and cars (5 m long) go on a single lane bridge. There must be a gap of at least 20 m after each truck and a gap of at least 15 m after each car. Trucks and cars travel at a speed of 36 km/h. If cars and trucks go alternately, what is the maximum number of vehicles that can use the bridge in one hour?

A. 1440  B. 1200  C. 720  D. 600

Accepted Answer

Maximum number of vehicles = 1440 (option A). Trucks and cars share a single lane and travel at the same speed (36 km/h = 10 m/s). Each vehicle occupies its own length plus the mandatory gap behind it. The key insight is that the effective 'slot' each vehicle takes up in a moving convoy determines how many vehicles pass a fixed point per second. Since cars and trucks alternate, we treat each truck-car pair as one repeating unit.