Question

A and B are two stations. A train goes from A to B at 64 km/hr and returns to A at a slower speed. If its average speed for the whole journey is 56 km/hr, at what speed did it return?

• A. 48 km/hr
• B. 49.77 km/hr
• C. 30 km/hr
• D. 47.46 km/hr

Answer 1

The correct option is B 49.77 km/hr

(b)
Let the required speed by x km/hr

$Then,\frac{2\times 64\times x}{64+x}=56$

$\therefore 128x=64\times 56+56x$

$\therefore x=\frac{64\times 56}{72}=49.77km/hr$