A 400-meter-long train crosses a 600-meter-long tunnel at the same time when another train twice as fast and half-length crosses a triple-length tunnel.

**Which train will (completely) leave the tunnel first?**

#### Solution

If we apply the formula: *speed = space / time* We have the time it takes for the first train to completely exit the tunnel is:

For the second train of half length: 200m, triple tunnel length: 1800 and twice the speed: 2v we have to:

**In other words, it takes exactly the same to get out of the tunnel.**