Question

On a 100 km track, a train travels the first 30 km at a uniform speed of 30 km/h. how fast must be the train travel the next 70 km so as to average 40 km/h for the entire trip?


Hey Ppl pls answer this!!!!!​

Answer 1

Answer:

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Answer 2

Explanation:

d₁ = 30 km

d₂ = 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

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 = d₂/t₂

⇒ 70/1.5

⇒ 46.666 km/hr or 46.7 km/hr

Hope it helps!