Two trains, each 150 m long, run in opposite directions and cross each other in 9 seconds. One train is twice as fast as the other. What is the speed of the faster train?

Explanation

1. 01

   Relative speed $= \frac{300}{9} = \frac{100}{3}$ m/s $= \frac{100}{3} \times \frac{18}{5} = 120$ km/h.

2. 02

   Speeds are $x$ and $2x$, so $3x = 120$, $x = 40$.

3. 03

   The faster train runs at 80 km/h.