Question

A car driver travels from the plains to the hill station, which are 200km apart at an average speed of 40 km/hr. in the return trip, he covers the same distance at an average speed of 20 km/hr. the average speed of the car over the entire distance of 400km is

Answer 1

time =distance/speed
so .....200 km/40=5hour
200/20=10 hour
so total time =15 and total distance=400
average speed of entire distances=400/15=26.66

Answer 2

GIVEN
DISTANCE = 200 KM
SPEED IN CASE 1
= 40 KM/H
THEN TIME TAKEN
= 200/40
= 5 H
NOW SPEED IN CASE 2
= 20 KM/H
THEN TIME
= 200/20
= 10 H

NOW
TOTAL TIME TAKEN = 15 H

AND

TOTAL DISTANCE = 400 KM

THEN SPEEDavg = 400/ 15
= 26.66 KM/H
OR
26.7 KM/H