A man drive his car to the office at 20 km/hr. After reaching office, he realize that its a new year holiday so he went back home at a speed of 30 km/hr.
Discounting the time spent in the stoppage what was his average speed of the journey ?
Answer is 24. we can calculate it using Harmonic Mean average speed = (2 x 20 x 30) / (20 + 30) = 1200 / 50 =24.
let distance between home and office is 20 km then total distance =20+20=40km total time = 1+2/3=5/3 hours average speed =total distance/total time =40/(5/3) =24km/hr
average speed of car=(2*20*30)/50 =24 km/hr
v=s/t => v = 40km/(5/3)h => v = 24km/h
A cyclist covers his outward journey at 15 mph.
The return, over exactly the same distance, is uphill. He completes it at 5 mph.
What is the cyclist's average speed over the entire journey?
An aeroplane maintains an average speed of 180 miles per hour from one airport to another airport. It then returns to the first airport over exactly the same distance at an average speed of 144 miles per hour. What was the average speed over the whole journey?
Early one morning a family travelled to a shopping centre at 35 km/h.
After a day of Christmas shopping they returned, over exactly the same distance, at a crawl of only 14 km/h.
What was their average speed over the entire journey?
A coach covers its outward journey at 50 mph.
It returns, over exactly the same distance at 33.3333 mph.
What is the average speed of the coach over the entire journey?
A helicopter covers its outward journey at 330 mph.
It returns over exactly the same distance at 220 mph.
What is the helicopter's average speed over the entire journey?
