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# A body covers half of the journey at 40km/hr and seconds half at 60 km/hr speed. Find the average speed of the whole journey

$(a)\;50\; km/hr \quad (b)\;48\; km/hr \quad (c)\;45 \;km/hr\quad (d)\;25\;km/hr$

$Average\; speed=\large\frac{total\; distance}{total \;time}$
Let $2s$ be the total distance
$Total \;time=\large\frac{s}{40}+\frac{s}{60}=\large\frac{s}{24}$
Therefore $Average\; speed =\large\frac{2s}{s/24}$
$=48 km/hr$
Hence the average speed of the whole journey is $48 km/hr$

edited Jun 20, 2013 by meena.p