Question

A train covers half of the journey with a speed of 30km/hr and other half with a speed of 40km/hr calculate its average speed for the entire trif

Answer 1

let total distance be 2x
in half of the journey distance becomes x
time for first half journey is dist./speed
t1=x/30
in the second half journey time becomes
t2=x/40

we know that,
average speed =total distance/total time
= 2x upon x/30+x/40
=2x/70x/1200
=2400/70
=240/7 ans.