Multiple choice

A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then find the length of the tunnel (in meters)?

  1. 630

  2. 320

  3. 500

  4. 550

  5. 540
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C Correct answer
Explanation

Speed = 78 km/hr = 78 * (5/18) = 65/3 m/s. Time = 1 minute = 60 seconds. Distance = Speed * Time = (65/3) * 60 = 1300 m. Tunnel length = Total distance - Train length = 1300 - 800 = 500 m.

AI explanation

Using the unitary method, convert the speed of 78 km/hr to metres per second by multiplying by 5/18 to get 65/3 m/s. The total distance covered in 60 seconds is the product of speed and time, which gives 1300 m. Subtract the train length of 800 m from this total distance to find the tunnel length of 500 m.

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