# How do I find average velocity over a given time interval?

May 17, 2015

Average velocity = total distance / total time

Example:
I travel from Rotterdam to Amsterdam (100 km) with an average speed of 80 km/h and return with an average speed of 120 km/h.

Then my average verlocity is NOT 100 km/h, but:

Time for the trip out: $\frac{100 k m}{80 k m / h} = 1.25 h$

Time for the trip back: $\frac{100 k m}{120 k m / h} \approx 0.83 h$

Total time: $1.25 + 0.83 = 2.08 h$ over $200 k m$

Average velocity: $\frac{200}{2.08} = 96.0 k m / h$

This may be counter-intuitive, but remember you spend more time in the slow mode than in the fast mode.