When a train passes through a tunnel, the total distance covered is the sum of the length of the tunnel and the length of the train. The speed of the train is given in km/hr, and the time is given in minutes, so unit conversion is necessary. The speed can be converted to meters per minute. Using the formula distance = speed × time, we can calculate the total distance covered. Subtracting the length of the tunnel from the total distance will give the length of the train.