Question

An aeroplane flies from A to B at the rate of 500 km/ hour and comes back from B to A at the rate of 700 km/ hour. The average speed of the aeroplane is......?

Answer 1

From A to B in `x` hours covers distance `500x` km

From B to A in `y` hours covers distance `700y` km

But since the distance back and forwards is the same

`500x=700y`

`y=5/7x`

Average distance =(total distance)/(total time)

Average distance =`(500x+700y)/(x+y)`

But `y=5/7x`

Hence

Average distance= `7000/12` km/hr