Question

A man travels at a speed of 20 km/hr and then returns at a speed of 30 km/ hr. His
average speed of the whole journey is :

Answer 1

Answer:

Step-by-step explanation:

Let the distance between A and B be the LCM of 20 and 30 which is 60km.

So, time taken in going from A to B = 60/20 = 3 hrs.

Time taken in coming back from B to A = 60/30 = 2 hrs.

Now,

Average speed = Total Distance/Total time taken = (60+60)/(3+2) = 120/5 = 24kmph

Answer 2

Answer:

Step-by-step explanation:

In statistical method or harmonic mean method. Here we use harmonic mean because of A.M>=G.M>=H.M.

Harmonic mean ( HM)= {2×a×b}/a+b

Here a=20 and b=30,

So by putting the value of a and b we get,

1200/50=24

So answer is 24 km/he.