27) C

Time taken by sound to travel in steel = t
Let time taken by sound to travel in air = t + 1.5

The distance travelled by the sound in steel would be the same as distance travelled by sound in air

Distance travelled by sound in air = (t + 1.5) x 300
Distance travelled by sound in steel = t  x 4800

300t + 450 = 4800t
450 = 4500t
t = 0.1 s

Distance of train = 4800 x 0.1 = 480 m