A man covers the journey from station A to station B at a uniform speed of 36 kmph and returns to A with a uniform speed of 45 kmph, his average speed for the whole journey is:

Explanation:-

Average speed for this case is given by,
[^2XY/_(X+Y)], where X and Y are two different speeds.
Average speed,
= [^{(2 * 36 * 45)}/_{(36 +45)}]
= ^(36*90)/₈₁. = 40 kmph.