Distance between two stations A and B is 778 km. A train covers the journey from A to B at 84 km per hour and returns back to A with a uniform speed of 56 km per hour. Find the average speed of train during the whole journey.
A. 60 km/hr
B. 30.5 km/hr
C. 57 km/hr
D. 67.2 km/hr
Show Answer
Answer-D
Solution-
Solution(By Apex Team)
The required average speed given by the formula,
$\begin{array}{l}\text{ Average speed }\\
=\Large\frac{2xy}{x+y} \small\mathrm{~km}/\mathrm{hr}\\
\text{Where,}\\
\text{x=84 km/hr}\\
\text{y=56 km/hr}\\
\text{Average speed}\\
=\Large\frac{2 \times 84 \times 56}{84+56} \\
=67.2 \mathrm{kmph}
\end{array}$
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