Question

a car travels from A to B at a speed of 20km/hr and returns at a speed of 30km/hr. The average speed of the car for whole journey is

Answer 1

Hi.

Here is your answer-----------

Let the distance between A and B is x km.
Speed of the car from A to B(u)  = 20 km/hr.

Therefore,
 time(T1) = x/20
Also,
Distance between B and A = x km.
Speed of the car from B to A(v) = 30 km/hr.
time(T2)= x/30

Thus,
total time = T1 + T2
               = x/20+ x/30
               = x/12 hr.
total distance covered by the car = x + x
                                                    = 2x
Using Formula,

Average Speed =  Total distance/Total time
                          =  2x/(x/12)
                          = 24 km/hr.

Thus, average speed of the car is 24 km/hr.

Hope it will help u.

Have a nice day.
            

Answer 2

Answer:

24 Kmph.

Explanation:

For MCQ's method ...

Vav=2×20×30÷20+30=24