Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. If one is moving twice as fast as the other, then the speed of the faster train is:

Length of each train= 100 m 

$\because$Total distance traveled by train to cross each other 

$=100+100=200\mathrm{m}$. 

Time is taken = 8 sec.

$\because$$\text{ Speed }=\frac{200}{8}=25\mathrm{m}/\mathrm{s}$

Let the speed slow. The train is x m is. 

$\because$The speed of fast train is 2x m/s.

$\begin{array}{l}\therefore \mathrm{x}+2\mathrm{x}=25\\ 3\mathrm{x}=25\\ \mathrm{x}=\frac{25}{3}\mathrm{m}/\sec \\ \mathrm{x}=\frac{25}{3}\times \frac{18}{5}=30\mathrm{km}/\mathrm{h}\end{array}$

So, speed of faster train = 2x = 2 x 30 

= 60km/hr.