Question

Distance between two stations a and b is 778km. A train covers the journey from a to b at 84 km per hour and returns back to a with a uniform speed of 56 km per hour. Find the average speed of train during the whole journey. 60 km/hr 30.5 km/hr 57 km/hr 67.2 km/hr

Answer 1

From a to b,

Distance=778km

speed=84km/hr

time= distance÷speed

=778÷84

=9.25hr

From b to a,

Distance=778km

speed=56km/hr

time=distance÷speed

=778÷56

=13.89hr

Av.speed=total distance÷total

time

=778+778÷9.25+13.89

=67.2km/hr