Tunnel

Kubo sits on a train speeding at 108 km/h. At that moment, the train enters the tunnel, which, according to Kub's book, is 2 km long. Kubo notices that the end of the train has left the tunnel 75 seconds later than the locomotive has entered the tunnel.
What is the length of the train in meters?

Correct answer:

x =  250 m

Step-by-step explanation:

$$\begin{gathered} v=108\text{km/h}\to \text{m/s}=108:3.6\text{m/s}=30\text{m/s} \\ a=2\text{km}\to \text{m}=2\cdot 1000\text{m}=2000\text{m} \\ T=75\text{s} \\ T=(a+x)/v \\ T\cdot v=a+x \\ x=T\cdot v-a=75\cdot 30-2000=250\text{m} \end{gathered}$$

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