A car travels at the speed of 50 km/hr for the first half of the journey and at the speed of 60 km/hr for the second half of the journey. What is the average speed of the car for the entire journey?

Let say, total distance of the journey is

d km .

He travelled half of the journey with 50km/h and rest of the half with 60 km/h.

So, time taken by the first half of journey is

$$=(1/50)×(d/2) hr=(d/100) hr.$$

and time taken by rest of the journey is

$$(1/60)×(d/2) hr=(d/120) hr.$$

So, average speed of the journey

(Total distance travel/Total time taken).

So,Average speed

$$=(d)/((d/100)+(d/120))$$

$$=d/((3d+2.5d)/300).$$

$$=300d/5.5d$$

$$=54.54$$

So A is correct choice.