A person travels in a car for 600 km at an average speed of 50 km/h and 100 km at 100 km/h, and finally reaches his destination by travelling 50 km at a speed of 25 km/h. Determine the average speed during the whole journey
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 50 km/h
Time = Distance/Speed
First part of the journey -
Distance = 600 km, Speed = 50 km/h
Time = 600/50 = 12 hr
Second part of the journey -
Distance = 100 km, Speed = 100 km/h
Time = 100/100 = 1hr
Third part of the journey -
Distance = 50 km, Speed = 25 km/h
Time = 50/25 = 2 hr
Total distance = 600 km + 100 km + 50 km = 750 km
Total time = 12 hours + 1 hour + 2 hours = 15 hours
Average speed = Total distance/Total time = 750/15 = 50 km/h