Sriya with her family travelled from Bolpur to Suri by car at a speed of 40 km/hr and returned to Bolpur at a speed of 50 km/hr. The average speed for the whole journey is :

September 1, 2016 September 1, 2016

Sriya with her family travelled from Bolpur to Suri by car at a speed of 40 km/hr and returned to Bolpur at a speed of 50 km/hr. The average speed for the whole journey is :
[A] $44\frac{4}{9}$ km/hr
[B] $44.78$ km/hr
[C] $45\frac{1}{2}$ km/hr
[D] $45$ km/hr

$\mathbf{44\frac{4}{9}}\ km/hr$
Average speed of journey =
$= \left ( \frac{2xy}{x+y} \right )\ km/hr$
$= \frac{2\times 40\times 50}{40+50} = \frac{400}{9} = 44\tfrac{4}{9}\ km/hr$
Hence option [A] is correct answer.