Question

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A train 100 m long is moving with a velocity of 72 km /h .Find the time it takes to cross a bridge which is 1 km long​​

Answer 1

GIVEN

• Length of the train = 100 m
• Velocity = 72 km/hr
• Length of Bridge = 1 km

TO FIND

• The time taken by the train to cross the bridge

SOLUTION

† Speed = 72 km/h

→ 72 × 5/18 = 360/18 = 20 m/s

† Total Distance = Length of Bridge + Length of Train

→ 1000 + 100m = 1100m

† Time = Distance/Speed

⟶ 1100/20 = 55seconds

★The time taken by the train to cross the bridge is 55 seconds.

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Answer 2

1km=1,000m

From the second the front nose of the train touches the bridge until the back-end of the train leaves the bridge, the train has to travel 300 meters.

The train travels 72km/h, or 72,000m/h.

72,000 % 300 means it will take 1/240th of an hour to cross the bridge.

1 hour has 3,600 second in it. 3,600 seconds % 240 (parts), means that it will take the 100m train 15 seconds to cross the 200m bridge.