A 120 meters long train cross a pole in 4.8 sec, then find in what time train will cross a platform, whose length is three times of the length of the train?

Let speed of train is S m/s

S = $frac{{120}}{{4.8}} = 25;{ m{m}}/{ m{s}}$

Let train will cross the platform in T sec

25 = $frac{{120 + 120 imes 3}}{T}$

25 × T = 480

T = $frac{{480}}{{25}}$ ⇒ T = 19.2 sec