Discussion Forum

A train X speeding with 120 kmph crosses another train Y, running in the same direction, in 2 minutes. If the lengths of the trains X and Y be 100 m and 200 m respectively, what is the speed of train Y ?

Answer:

Explanation:

Let the speed of train $Y$ be $x$ km/hr.

Speed of $X$ relative to $Y$ $=(120-x)$ km/hr.

$=\left[(120-x)\times\frac{5}{18}\right]$ m/sec $=\left(\frac{600-5x}{18}\right)$ m/sec.

$\therefore$ $\frac{300}{\left(\frac{600-5x}{18}\right)}=120$ $\Leftrightarrow 5400=120(600-5x)$

$\Leftrightarrow x=111$.