An electric train moving at 20km/hr acceleration to a speed of 30km/hr in 20seconds. Find e average acceleration in m/s^2 the distance traveled during the period of e acceleration?

The acceleration is given by the change in speed divided by the time over which that change occurs
  a = (30 km/hr - 20 km/hr)/(20 s) = 10/20 km/(hr*s)
  = (1/2)*(1000 m/km)*(1 hr/(3600s))*km/(hr*s)
  = 5/36 m/s^2
The average speed during the 20 second period of acceleration is
  (20+30)/2 = 25 km/hr = 25/3.6 m/s.
In 20 seconds, the train will have traveled
  (25/3.6 m/s)*(20 s) = 500/3.6 m = 138 8/9 m