Question

On A 90 kilometre track A train travels the first 30 km at a uniform speed of 30 km per hour how fast must the train travel the next 60 km so as to an average speed of 60 km per hour for the entire trip​

Answer 1

Answer:

As the total distance = 90 km

Average speed = 60 kmph 

Total time duration = 90 / 60 = 3/2 hours

 

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

Hence, time remaining to cover the remaining 60 km = 3/2 hrs - 1 hrs

= (3-2)/2 hour

= 1/2 hr.

 

Speed during 60 km  = 60*2 = 120km/hr

Answer 2

total distance =90km.

avarage speed = 60km/hr

total time = 90/60= 3/2hr

distance 1 = 30km/hr

Speed 1 = 30km/hr

time taken = 30/30=1hour

time left = 3/2-1=1/2hour

Speed 2 = 60/(1/2)=120km/hr