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 kmph. If cars and trucks go alternatively. What is the maximum number of vehicles

that can use the bridge in one hour?
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Answer 1

Answer:

Given speeds both car & Truck = 36 km/hour

They travel in 1 hr = 36 km = 36000 m.

∴ Maximum no. of vehicles than can use the bridge  in 1hour =36000m50m=720sets=720×2=1440 vechicles  Alternate method ∴ Maximum no. of vehicles than can use the bridge  in 1hour =36000m50m=720sets=720×2=1440 vechicles  Alternate method 

 Length of truck + gap required =10+20=30m Length of car + gap required =5+15=20m Alternative pairs of Truck and car needs 30+20=50m .  Length of truck + gap required =10+20=30m Length of car + gap required =5+15=20m Alternative pairs of Truck and car needs 30+20=50m . 

 Let'n' be the number of repetition of (Truck + car) in 1 hour (3600 sec).  Given speed =36km/hr=10m/sec50m×n3600sec=36km/hr Let'n' be the number of repetition of (Truck + car) in 1 hour (3600 sec).  Given speed =36km/hr=10m/sec50m×n3600sec=36km/hr

⇒50n3600m/sec=10m/sec⇒n=3600050=720( Truck +ear )⇒50n3600m/sec=10m/sec⇒n=3600050=720( Truck +ear )

720( Truck + car ) passes =720×2=1440720( Truck + car ) passes =720×2=1440 vehicles

Hope this helps