Correct Answer - Option 3 : 500 m

**Given : **

length of train 1 = 200 m

Speed of train 1 = 90 km/hr = 25 m/s

Speed of train 2 = 108 km/hr = 30 m/s

**Calculations :**

Let the length of tunnel be x m and length of the second train be L_{T}

According to question first train takes 24 sec to pass the tunnel so,

⇒ (200 + x)/25 = 24

⇒ x = 400 m

∵ it is given that train 2 passes the tunnel in 30 s

⇒ ( L_{T} + x )/30 = 30

⇒ (L_{T} + 400)/30 = 30

⇒ L_{T} = 500 m

**∴ The length of the second train is 500 m.**