Question

On a 120 km track train moves the first 30km at uniform speed of 30km/hr .how fast must the train travel in next 90km.So as to have average speed 60km/hr for the entire trip​

Answer 1

   as the total distance = 120 km

   average speed = 60 kmph 

       => total time duration = 120 / 60 = 2 hours

 

   time taken for the first 30 km =  30 km /30 kmph = 1 hours

   Hence, time remaining to cover the remaining 90 km = 2 hrs - 1 hrs = 1 hour

   => speed during 90 km  = 90 kmph

hope it helps..