A train traveling at 100 km an hour takes 3 seconds to enter a tunnel and an additional thirty-five seconds to pass completely through it. Find the length, in kilometers, of the train. Express your answer as a common fraction.

Let the length of the train ==T

Distance ==average speed x time.

T ==3/3,600 x 100 ==1/12 km - length of the train.

Let the length of the tunnel ==t

t ==35/3,600 x 100 ==35 / 36 km - length of the tunnel.