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.
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