Question

On a 120 km track train travel first 30 km at 30 km/hr.How fast the the train should travel the rest distance to have avg. speed of 60 km/hr

Answer 1

Hii..
Here is your answer..

Solution:-
Total length of track was=120km
Average speed=60km/h
Time =?
Since we know that,
$average \: speed = \frac{total \: distance}{total \: time \: taken}$
So,
$time = \frac{total \: distance}{average \: speed} \\ = > \frac{120}{60} \\ = > 2hrs$
Now,
First he travelled Distance=30km
Speed was=30km/h
So,
Time would be =D/S
$= > \frac{30}{30} \\ = > 1hrs$
The remain Distance=120-30=90km
So,
Second Distance he travelled=90km
Let the speed be x
Therefore,
Time =D/S
$= > \frac{90}{x}$
A/q
$= > 2 =1 - \frac{90}{x} \\ = > 2 - 1 = \frac{90}{x} \\ = > 1 = \frac{90}{x}$
$= > x = 90$
=>90km/h

Hence,he should travelled the remain 90km at speed of 90km/h so that average speed would be 60km/h

Hope it helps uh...✌️✌️✌️