Question

on a 120 km track a train travels the first 30 km at a uniform speed of 30km/ h. calculate the speed with which the train should move rest of the track so as to average speed 60km/h for the entire trip

Answer 1

hope this helps uuuuuuuuuu

Answer 2

Here's your answer !!

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We know that,
$average \: speed = \frac{total \: distance \: travlled}{total \: time \: taken}$
Average speed =60km/h
distance travelled=120km
let time taken be x.
So,
$= > 60 = \frac{120}{x} \\ = > x = \frac{120}{60} \\ = > x = 2hrs$
Now,
In first case:-
Distance travelled=30km
Speed = 30km/h
So,
Time taken =Distance/Speed
$= > \frac{30}{30} = 1hrs$
In Second case :-
Distance travelled=90km
Speed = let it be x
So,
Time taken
$= > \frac{90}{x}$
Now,
A/q
$= > 2 = \frac{90}{x} + 1 \\ = > 2 - 1 = \frac{90}{x} \\ = > 1 = \frac{90}{x}$
$= > x = 90$
Hence,
The train must travel at speed of 90km/h to rest 90km so that average speed is 60km/h for while journey.

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Hope it helps you!! :)