A train travels from a city A to city B with a constant speed of 10 m/s and returns back to city A in half of the time taken to travel from A to B. Find its average speed during the entire journey. A) 40 m/s B) 30 m/s C) 15 m/s D) 40 3 m/s

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A train travels from a city A to city B with a constant speed of 10 m/s and returns back to city A in half of the time taken to travel from A to B. Find its average speed during the entire journey.   A) 40 m/s   B) 30 m/s   C) 15 m/s   D)         40     3     m/s

reescameriama10 · Accepted Answer

The correct answer is D)         40     3     m/s  Let distance between the two cities A and B be x m.  Speed of train while going from A to B=10 m/s  Time taken by train to travel from A to B           t     1      =        x     10      and time taken by train to travel from B to A          t     2      =               t       1          2      =        x     20      Average speed    =        total distance     total time              v            a       v       g           =               x       +       x                          x         10              +                x         20                  Hence,         v            a       v       g           =               2       x                          x         10              +                x         20                  =        40     3      m        /      s

A train travels from a city A to city B with a constant speed of...

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