Question

on a 120 km track A train travels the first 30 km at a uniform speed of 30 km per hour.Calculate the speed with which the train should move rest of the track so that its average speed for the entire trip is 60 km per hour?​

Answer 1

Explanation:

Average speed=Total distance Total time taken

V

av

=

t

d

ort=

V

av

d

For 120 km,

t=

60 km/hr

120 km

=2 hr ......(i)

For 1st 30 km,

t

1

=

30 km/hr

30 km

=1 hr

For remaining 90 km,

t

2

=t−t

1

=2−1=1 hr

speed=

time

distance

or v

2

=

t

2

d

2

=

1

90

=90 km/hr