Question

Abdul,while driving to school,computes the average speed for his trip to be 20 km/hr. On his return trip along the same route there is lees traffic and the average speed is 4 km/hr. What is the average speed for Abduls trip

Answer 1

Hii..
Here is your answer...

Solution:-
Let the one way Distance be x km

Time taken in forward trio at speed if 20km/h
$= > \frac{distance}{speed} = \frac{x}{20} h$
Time taken in return trip at a speed of 4km/h
$= > \frac{x}{4}h$
Time taken for whole trip =
$= > \frac{x}{20} + \frac{x}{4} \\ = > \frac{x + 5x}{20} \\ = > \frac{6x}{20}$
Total Distance travelled=
$= > x + x \\ = > 2x$
Now,
$average \: speed = \frac{total \: distance}{total \: time}$
$= > \frac{2x}{ \frac{6x}{20} } \\ = > \frac{2x \times 20}{6x} \\ = > \frac{120x}{6x} \\ = > 20$
Hence,
Average speed is 20km/h

Hope it helps uh...✌️✌️✌️

Answer 2

distance on going =distance on returning=d
speed while going = 20km/h
speed while returning =4km/h
time taken while going = distance/speed
=d/20
time taken while returning=distance/speed
=d/4
avg. speed=total distance/total time
=(d+d)/(d/20+d/4)
=2d/(d+5d)/20
=2d/6d/20
=2d/6d*1/20
=1/60km/h=5/18*1/60m/s=1/1080m/s