calculating acceleration of a train

change in velocity=acceleration*time

v1=10 mph

v2=70 mph

60 m/h=acceleration*5 minutes

You either have to convert minutes to hours, or hours to minutes. I would do the former. Then solve for acceleration.

The train accelerated at a net 60 miles/hour per 5 minutes in an unknown direction is all you can say.

You don't know if acceleration is constant or not, if the observed speed was its maximum, median, medium during its travel, you don't know if its experiencing angular acceleration.

Tie the question better if you want to here folk say oh in 300 sec it accelerated at a constant 60KM/h so its accelerating at 1/5 km/hr/sec

Yes, the best you can do is give the average acceleration. I suspect that direction vector is not an issue.