physics
posted by srikala .
a train moving at constant velocity of 54 k mph moves east wards for 30 min, then due to north with the same speed for 40 min. What is the average velocity of the train during the run?(in k mph)

I assume that your "k mph" is really kilometers per hour (km/h)
In 70 minutes, the train goes (1/2)*54 = 27 km east and (2/3)*54 = 36 km north.
It ends up sqrt[(27)^2 + (36)^2]= 45 km from where it started.
The magnitude of the average velocity
is 45 km/(7/6 h) = 38.57 km/h
(70 minutes = 7/6 hour)
The direction of the avg velocity is
arctan 36/27 = 53.13 degrees north of east. 
Kmph