Finding the Average Speed Using the Harmonic Mean
Formula
When traveling a distance $S$ at speed $a$ and returning at speed $b$, the average speed $v$ can be represented as the harmonic mean of the two speeds. $$ v = \frac { 2ab }{ a+b } $$
When traveling a distance $S$ at speed $a$ and returning at speed $b$, the average speed $v$ can be represented as the harmonic mean of the two speeds. $$ v = \frac { 2ab }{ a+b } $$