If I drive x mph for t hours and then y mph for 2t hours, what is the expression for average speed?
I know the average speed = distance/time but that's where I get stuck.
Or... d = rt.
If you drive x mph for t hours, then the distance traveled is xt miles.
If you drive y mph to 2t hours, then the distance traveled is 2yt miles.
Total distance: xt + 2yt.
Total time: t + 2t = 3t.
Average speed:
$\displaystyle \frac{xt + 2yt}{3t} = \frac{x + 2y}{3}$
01
Edit: beaten to it by three people!