As the speed is constant, we can use the rule of three to calculate how far itgoes in 1 min.
If it goes 7.5 km in 6 min:
![\begin{gathered} 6\min \longrightarrow7.5\operatorname{km} \\ 1\min \longrightarrow x=7.5\operatorname{km}\cdot(1\min)/(6\min)=(7.5)/(6)=1.25\operatorname{km} \end{gathered}]()
NOTE: If we want to calculate how far it goes in 100 minutes, we apply the same rule:
![\begin{gathered} 6\min \longrightarrow7.5\operatorname{km} \\ 100\min \longrightarrow x=7.5\operatorname{km}\cdot(100\min )/(6\min )=(750)/(6)=125\operatorname{km} \end{gathered}]()
Or we can just multiply 1.25 km/min, which is the speed, by 100 min, and get 125 km.
Answer: The train will travel 1.25 km in one minute.