Question

On a 100km track, a train travels the first 30km at a uniform speed of 30km/hr. How fast

must the train travel the next 70km, so as to average 40km/hr for the entire trip​

Answer 1

Answer:

Given :

➡Distance 1 = 30 km

➡Distance 2 = 70 km

We know that speed = distance/time

and, Average speed = total distance/total time taken

When the train acquired a speed of 30 km/hr, the time taken = 30/30 = 1 hour

Average speed = (distance 1 + distance 2)/(time 1 + time 2)

AS time 2 or t2 is time taken for the second part of the journey of 70 km

⇒ 40 = 100/(1 + t2)

⇒ 40 + 40t2 = 100

⇒ 40t2 = 100 - 40

⇒ 40t2 = 60

⇒ t2 = 60/40

t2 = 1.5

So, t2 or time taken to travel the second part of the journey is 1.5 hours.

Speed of the second part of the journey = distance 2/time 2

⇒ 70/1.5

⇒ 46.666 km/hr or 46.7 km/hr

Explanation:

Hope this helps please follow

Answer 2

Answer = 46.67 km/h

FORMULAE USED:-

# average speed = Total distance/Total Time

HOPE IT HELPS....