Basic Algebra Question about speed Hi I just want to check this.  It's from a recent test I took and the answer I got didn't match any of the choices.  If a car travels $x$ miles at $Y$ miles per hour, and then another $x$ miles at $Z$ miles per hour, what is the average speed during the trip?  It should just be the total miles divided by the total time right?  That's $$\frac{2x}{\frac{x}{Y} + \frac{x}{Z}}$$
Be careful about average velocity and average speed. If you want to calculate average speed, then your calculation is ok. But average velocity is   $ \frac{displacement}{time}$. So if the car moves x miles to the east and then x miles to the west, then the average velocity is $0$.
Be careful about average velocity and average speed. If you want to calculate average speed, then your calculation is ok. But average velocity is   $ \frac{displacement}{time}$. So if the car moves x miles to the east and then x miles to the west, then the average velocity is $0$.