Question

On a 120 km track , a train travels travels the first 30 km at a uniform speed of 30km/h. how fast must the train travel the next 90 km so that the average total speed for the trip is 60km/h

Answer 1

also write first the following
average speed = total distance /total time
60 = 120/ total time
and total time = 120/60 hrs
=2hrs

Answer 2

$avg. \: speed =( speed1 + speed2) \div 2$
$60 = (30 + x) \div 2$
$30 + x = 40 \times 2$
$30 + x = 120$
$x = 120 - 30$
$x = 90kmph$
$therefore \: for \: average \: speed \: to \: be \: equal \: to \: 60kmph \: the \: train \: shoud \: travel \: at \: the \: speed \: of90kmph$
$\\ \\ \\ hope \: that \: this \: is \: the \: required \: answer$